Why is it that this argument is invalid? Is it because some almonds might not necessarily be exported to Brazil because of the differences in sizes of the sets? #help

I didn't pick C because it has the year range as 1981-1990 instead of 1986-1990. Can anyone please explain why it would still be right despite this date range? Thanks!

On question 3, why is "existence of black holes" not the object in the predicate?

I didn't pick A because I thought stating that a few workers from Plant B eating nutritious breakfast would weaken the results. I thought that by saying a few employees ate a nutritious breakfast, that it would impact the productivity levels or results in some way, rather than if it said that "none" of them ate a nutritious breakfast. Why isn't this the case?

How can we pinpoint the word whose meaning may change for questions like this? I kept A alive, but did not pick it because I thought it referred to another word, not anarchy.

If the argument is saying that data on the weed killers is likely misleading, wouldn't option D support that idea? I'm still not sure why D would be a weakening choice as opposed to a strengthening one

These "weakening" questions are confusing to me because I thought we weren't supposed to be making assumptions about answer choices. Is it only for the "must be true" questions that we shouldn't be assuming anything? If so, does anyone have any tips for generating assumptions for questions like this one?