If energy efficiency is improved, the cost of energy would decrease and a)more coal would be available
b) less electricity would be used
c) homes would cost significantly less
d) energy star appliances would no longer be necessary

The correct answer is option B

The energy efficiency can be defined as the output of energy to the input of energy.

As the efficiency of energy is increasing then the consumption of electricity will be less because previously the energy was used more due to loss of energy.

But now the energy will not be lost in the form of heat or friction and the cost of energy will be less.