A scientist wants to test whether the pH, salinity, or temperature of seawater impacts coral development. He sets up an experiment with three conditions: Aquarium 1: Normal pH, normal salinity, normal temperature
Aquarium 2: High pH, high salinity, high temperature
Aquarium 3: Low pH, low salinity, low temperature

What factor would improve experimental design the most? (3 points)

Select one:
a. Eliminating Aquarium 1 since it only uses normal conditions
b. Testing one variable at a time and keeping the other two variables constant
c. Using one aquarium and changing the variables from day to day
d. Setting up the variables on a gradient in each aquarium
Please add an explanation this is marine science I will give brainliest to right answers