Question

question 4 of 5
the ph indicator bromothymol blue turns yellow when co₂ gas is added to a solution and blue when co₂ is removed from a solution. an experiment will test how the intensity of light affects the rate of photosynthesis in algae. which of these should be a control for this experiment?
a. algae that are placed in a blue solution and kept in the dark
b. algae that are placed in a blue solution and kept in direct sunlight
c. algae that are placed in a yellow solution and kept in direct sunlight
d. algae that are placed in a yellow solution and kept in the dark

Explanation:

In an experiment testing the effect of light intensity on photosynthesis rate in algae, the control group should have no light (to eliminate the variable of light) and a blue solution (indicating no CO₂ added initially as the indicator is blue when CO₂ is removed). This allows comparison with experimental groups that have different light intensities.

Answer:

A. Algae that are placed in a blue solution and kept in the dark