A marine biologist wishes to test the hypothesis that heavy grazing by fish causes the brown alga Laminaria to stay short rather than grow upright. Which of the following variables could be manipulated successfully at the shore to test this hypothesis?

A.

add nutrients to the ocean water around the algae to see if it will grow taller

B.

increase the amount of dissolved carbon dioxide in the water around the algae to see if they grow taller

C.

place a netted screen around the algae to restrict fish from grazing on the algae and check for any change in growth

D.

alter the intensity of light to see if this is the cause of the algae's stunted growth

E.

protect the algae from ocean waves to see if wave shock is causing the stunted growth

B.

increase the amount of dissolved carbon dioxide in the water around the algae to see if they grow taller

The correct answer is C. Place a netted screen around the algae to restrict fish from grazing on the algae and check for any change in growth

Explanation:

In an experiment, scientists commonly study different variables or factors to analyze a natural phenomenon. In this case, the two variables analyzed are the fish that eat the alga and the alga growth. This implies to test the hypothesis the biologists, need to manipulate or change any of these and thus, the best to test the hypothesis is "Place a netted screen around the algae to restrict fish from grazing on the algae and check for any change in growth" because in this way, the biologist can prove if the fish had any effect on the alga growth and also this variable can be easily manipulated.