23. Christina wanted to know whether the eating behavior of goldfish is affected by music. She set up a fish tank. Every day, she played music for the fish and measured how much the fish ate. What is Christina

missing from this experiment?

A. a control group

B. a measurable result

C. a dependent variable

D. different types of fish

Two kilograms of air within a piston–cylinder assembly executes a carnot power cycle with maximum and minimum temperatures of 800 k and 300 k, respectively. the heat transfer to the air during the isothermal expansion is 60 kj. at the end of the isothermal expansion the volume is 0.4 m3. assume the ideal gas model for the air. determine the thermal efficiency, the volume at the beginning of the isothermal expansion, in m3, and the work during the adiabatic expansion, in kj.