Question

after a two - day fishing tour at a local lake, it was observed that in one part of the lake the bass caught were unusually small in mass. a large manufacturing factory was releasing hot water into the lake at this point. a group of ecology students wanted to know if there was a relationship between the water temperature, the mass of the fish, and the amount of oxygen present in the water. the students set up four tanks and stocked each with 3 bass. which of the following must be the independent variable in this investigation?
a water temperature
b initial mass of the fish
c amount of food
d number of fish

Explanation:

In an experiment, the independent variable is the factor that is deliberately changed. Here, the students are looking at the relationship between water temperature (which is being potentially affected by the factory's hot - water release) and other factors (mass of fish, amount of oxygen). The water temperature is the variable that can be manipulated or is the starting point of the investigation. The mass of the fish (initial mass or final mass), the amount of food, and the number of fish are variables that might be dependent on other factors like water temperature.

Answer:

A. Water temperature