【单选题】The use of heat pumps has been held back largely by skepticism about advertisers' claims that heat pumps can provide as many as two units of thermal energy for each unit of electrical energy used, thu...
A.
explain the differences in the working of a heat pump when the out-door temperature changes
B.
contrast the heating and the cooling modes of heat pumps
C.
describe heat pumps, their use, and {actors affecting their use