Question

Three students each added equal volumes of pond water to four beakers and placed each beaker in a different water bath. Each student maintained the water baths at temperatures shown in the data table below. The students then added an equal number of water fleas to each of the four beakers. After one hour, the students used microscopes to determine the average heart rate of the water fleas. The procedure was repeated for a total of three trials at each temperature. The results of the investigation are summarized in the data table below.
Which component of the experiment above is the independent variable?


A. average water flea heart rate

B. number of fleas per beaker

C. number of trials

D. water temperature

Answer 1

Answer: D. water temperature

Explanation:

An independent variable is the something which can be altered or manipulated while doing an experiment so as to determine the effect of such change over the other variable that is the dependent variable or the experimental variable.  

Here, in the given experiment the water temperature is the independent variable whose effect can be observed on the dependent variable that is the average water flea heart rate.  

Answer 2

The independent variable is the water temperature because it is not dependent on the change of another variable so the answer would be D