The question stem says, which one of the following most accurately expresses the main conclusion of the argument?

So this is a main conclusion question.

Let's identify the line that we think is a conclusion and then look for an answer that best restates that line.

And so right off the bat, we have a recommendation from the author.

We should try to use double-blind techniques whenever possible in these experiments.

And because this is a recommendation, I'm already thinking this is a potential conclusion.

If the author follows up with reasons for why we should try to use double-blind techniques whenever possible,

then that will confirm that the first sentence is a conclusion.

So let's see what the author gives us.

Why should we believe that double-blind techniques should be used whenever possible in scientific experiments?

Because they can help prevent the misinterpretations that often arise

due to expectations and opinions that scientists already hold.

And, clearly scientists should be extremely diligent in trying to avoid such misinterpretations.

And these two statements here are giving me reasons that we should use double-blind techniques.

First, they help prevent misinterpretations that arise from expectations and opinions.

And then second, we should be trying to avoid those misinterpretations.

So put those two ideas together and that means, to the author, that we should try to use double-blind techniques.

So the last two lines here are premises.

We have two premises that support a conclusion in the first sentence.

Now I know that one point of confusion is going to be whether this very last part

about how scientists should be extremely diligent in trying to avoid misinterpretations,

whether that's a conclusion.

Because it actually is an opinionated line.

We have another recommendation.

Scientists should try to avoid these misinterpretations.

So naturally you might think, couldn't that be a conclusion?

But the problem is, we don't get any support for that last claim.

If you ask the author,

wait, why should scientists try to be diligent in avoiding misinterpretations?

There's no other line that helps explain why we should try to avoid misinterpretations.

The author just says we should try to avoid it.

So that's what tells you that this last part cannot be a conclusion because it doesn't have support.

What's happening here is the author is using the idea that we should try to avoid misinterpretations,

combining that with the fact that double-blind techniques help prevent misinterpretations,

and together those ideas are reasons that we should use double-blind techniques whenever possible.

So the conclusion is the first sentence here.

The other two lines are premises.

So let's go to these answers, and I'm looking for the answer that best restates

double-blind techniques should be used whenever possible in scientific experiments.

on the basis of expectations and opinions already held.

Okay, that may or may not be supported by what the author said,

but that is not a restatement of the bracketed line.

A isn't even saying anything about double-blind techniques and whether we should use them.

So that's why A is not correct.

in as high a proportion of their experiments as they can.

And yes, this is the right answer.

This is just a rephrasing of the first sentence.

We should use double-blind techniques in scientific experiments whenever possible.

Well, another way to say that is, it is advisable, or in other words,

it is something they should do to use double-blind techniques

in as high a proportion of their experiments as they can.

That means, whenever possible, you should use the double-blind techniques.

Use it in as high a proportion as possible means you should use it whenever possible.

So B is an exact match to the meaning of the first sentence.

They're just trying to throw you off by using different words to express the same idea.

Let's understand why the other ones are wrong now.

Okay, that may or may not be true.

Maybe it's supported by what the author said,

but it can't be correct because it is not restating the first sentence.

The first sentence is a conclusion.

We are just looking for an answer that expresses the first sentence,

and C does not do that.

scientists should refrain from interpreting evidence

on the basis of previously formed expectations and convictions.

Okay, that may be true.

That is part of the reasoning of the author.

Maybe you could say that that's an assumption,

but none of that matters because it is not a match to the first sentence.

The first sentence is a conclusion,

so we just want an answer that says the first sentence.

I think if you're tempted by any of the wrong answer here,

you are being attracted to answers that sound like the author would agree with them.

And sure, maybe the author would agree with them.

Maybe the author, in fact, did say them,

or that's part of the reasoning, or that's an assumption of the argument.

But we're being asked for the conclusion,

not just to pick something the author agrees with.

So D is not the conclusion, it is not restating the first sentence.

are often an effective way of ensuring scientific objectivity.

Okay, so I don't want to get into

whether ensuring scientific objectivity is like an appropriate phrase here.

Let's just say answer choice E sounds like something the author would agree with.

It's still not correct because it is not a restatement of the first sentence.

The first sentence is a recommendation that we should use these techniques

whenever possible in these experiments.

E does not say that we should use techniques.

It just says they're often effective.

Now probably the author thinks that they're effective,

and that is in part why the author thinks we should use these techniques,

but that doesn't make E correct

because E is not saying we should use the techniques.

The only answer that comes anywhere close to saying

we should use these techniques whenever possible

is answer choice B, and that's why B is correct.