To Check the Effect of Cold Temperatures on the Battery's

To check the effect of cold temperatures on the battery's ability to start a car researchers purchased
A battery from Sears and one from NAPA. They disabled a car so it would not start, put the car in a
Warm garage, and installed the Sears battery. They tried to start the car repeatedly, keeping track of
The total time that elapsed before the battery could no longer turn the engine over. Then they
Moved the car outdoors where the temperature was below zero. After the car had chilled there for
Several hours the researchers installed the NAPA battery and repeated the test. Is this a good
Experimental design?

A) No, because they should have tested other brands of batteries, too.
B) No, because the car and the batteries were not chosen at random.
C) No, because temperature is confounded by brand.
D) Yes
E) No, because they should have tested more temperatures.