Question

A student has several pet hermit crabs. He wants to determine how the hermit crabs choose which shell they inhabit. He thinks that the crabs choose their shells based on the shells' color and wants to design an experiment to test this. Which of these steps should the student include in his experiment? A. He should add shells that are different colors, but the same size and type, to the tank and observe which shells the hermit crabs choose. B. He should observe hermit crabs in their natural environments and determine how shells help protect them from predators. C. He should place the hermit crabs in different tanks and change the temperatures in the tanks to see if it effects their shell selection. D. He should gather shells that are different sizes and different colors, place them in the tank with the hermit crabs, then observe which shells they choose. Reset Next Question

Answer 1

A. He should add shells that are different colors, but the same size and type, to the tank and observe which shells the hermit crabs choose.

Durning an experiment you need to keep everything the same but only change the certain things based on your theory.
Such as how the student wanted to see if the color attracted the crab. If he had changed the size and type of the shell then the crab would have chosen the bigger one as they tend to grow into larger shells.