Strengthen the hypothesis

Some reading questions describe a situation and then state a hypothesis — someone's proposed explanation for what is going on.
The question asks which finding, if true, would most strengthen that hypothesis.
To strengthen means to make the explanation more likely to be correct; you are not proving it for certain, just adding support.

The key move is to ask: if this hypothesis were true, what would we expect to see?
In other words, what does the hypothesis predict?
The best answer is the choice that matches that prediction and rules out other explanations.

It helps to sort the choices into three groups.
A choice that supports the hypothesis lines up with its prediction.
A choice that weakens it points the other way.
A neutral choice may be true but has nothing to do with the hypothesis.
Only a supporting choice can be the answer, so cross out the weakening and neutral ones.

Here is the format you will see.
Passage: "A café owner notices that on days when she bakes fresh bread, the café is busier. She hypothesizes that the smell of fresh bread draws more customers inside."
Question: which finding, if true, would most strengthen her hypothesis?
Choice (A): "On days with fresh bread, far more people who were just passing by came in, but the café's regulars came the same as always."
Choice (B): "The café also runs a discount on coffee every morning."
Choice (A) strengthens the hypothesis, because new passers-by coming in fits the idea that the smell pulls people off the street.
Choice (B) is neutral — a coffee discount is a different possible reason for the crowd, so it does not support the smell idea.

A biologist studies a species of frog that has strikingly bright red-and-yellow skin. She knows that in many animals, bright colors act as a warning that the animal is poisonous to eat. She hypothesizes that these frogs evolved their bright colors to warn predators that the frogs are toxic.
Which finding, if true, would most strengthen the biologist's hypothesis?
(A) Birds that eat one of these bright frogs become ill, and afterward those birds avoid frogs with the same bright colors.
(B) The frogs are found only in a small rainforest region in Central America.
Choice (A) strengthens the hypothesis, because it shows the bright colors actually work as a warning tied to the frogs being toxic.
Choice (B) is neutral: where the frogs live tells us nothing about why they are brightly colored.

In a coastal town, residents notice that the ocean waves sometimes glow a bright blue at night. Scientists studying the water find tiny floating organisms called plankton that are able to produce light. The scientists hypothesize that these plankton light up specifically when the water around them is disturbed or stirred up.
Which finding, if true, would most strengthen the scientists' hypothesis?
(A) The glow appears only where waves crash on the shore and boats cut through the water, while calm stretches of the sea stay completely dark.
(B) The same kind of plankton has been found in oceans all around the world.
Choice (A) strengthens the hypothesis, because the glow shows up exactly where the water is being stirred and is absent where the water is still.
Choice (B) is neutral: how widespread the plankton are says nothing about what makes them light up.

A literature teacher is reading a novel whose main character, Sam, is born at the exact moment his country wins its independence. As the story unfolds, several major events in Sam's life seem to happen alongside major events in the nation's history. The teacher claims that the author deliberately shaped Sam's life to mirror the story of the country itself.
Which quotation from the novel, if included, would most strengthen the teacher's claim?
(A) A passage in which the turning point of Sam's life falls on the very same day his country signs a historic peace treaty.
(B) A passage that describes, in loving detail, Sam's favorite meal from childhood.
Choice (A) strengthens the claim, because it directly ties a personal turning point to a national event, just as the "mirror" idea predicts.
Choice (B) is neutral: a favorite childhood meal is a personal detail with no link to the country's history.