The words "only," "always," and "must" exclude everything else that is possible. For instance:

"My plants will grow only if I water them."

Because we see the word "only," this means that if I do not water my plants, they will not grow. For me, it's easier to understand if I start with the contrapositive.

/W>/PG

Based on the form of this argument, we know that watering the plants is the necessary condition for the plants to grow. My plants growing is the sufficient condition for me watering them. You can then flip this into:

PG>W

If my plants grow, then I watered them.

If the word "only" was not included in the original argument, then we would have:

"My plants will grow if I water them."

Because we do not see the words "only," "always," or "must," we know that the plants can grow even if I don't water them. This flips the conditions around:

W>PG

Watering the plants has now become the sufficient condition, because we know from the absence of "only," "always," and "must" that my plants could grow without watering. The contrapositive of this would be:

/PG>/W

If my plants do not grow, then I did not water them.

The necessary condition in this second argument is the plant growth. Me watering the plants is sufficient for the plants to grow, but the plants growing is not sufficient enough for me to know that I watered them.

I hope this helps.

The tiger argument is flawed because the argument assumes that a mammal which causes injury to people is unsuitable to be a pet.

The representation of other mammals in the tiger argument is a moot point, because the conclusion is that not all mammals are suitable pets. If it is true that one mammal is not suitable as pets, then the conclusion is also true that not all mammals are suitable as pets.

The argument is weak because it assumes that aggression and causing injuries to people makes being a pet unsuitable for that mammal. Remember, what we know about the real world doesn't matter. We know that violence makes a mammal unsuitable to be a pet, but the argument gives no evidence to support that, making it weaker than the Disney argument.

ignore

It is also not entirely certain that Alice will win the prize. What if Alice is disqualified, or must leave the competition for whatever reason before the prize is given? All the language on the LSAT is chosen for a reason, the these qualifying statements such as "almost," "mostly," "few," are important to watch out for