Answer:
variation in ambient / surrounding environment temperature
Step-by-step explanation:
An independent variable can be described as a variable which is being changed by nature or by the researcher to study its effect on the dependent variable. In the experiment being performed, thermoregulation in crickets is the dependent variable. The variations which we will make in the surrounding atmospheres to check its effect on the differences in thermoregulation will be the independent variable for our experiment. Hence, option D is correct.