All are TRUE regarding Net Protein Utilisation, except –
Net protein utilization 

NPU is the percentage of ingested protein retained inside the body (not an increase in weight)
It is a product of digestibility coefficient and biological value divided by 100.
The protein requirement varies with the NPU of dietary proteins. If the NPU is low, the protein requirement is high, and vice versa.
NPU of protein for Indian diets varies between 50 and 80.
NPU is 100 for egg (best protein) and about 75 for milk

NPU = Retained nitrogen / Nitrogen of food x 100
NPU = Digestibility coefficient x Biological value / 100
About option 'a'
Increase in weight per unit weight of protein consumed is known as protein efficiency ratio.
It is the increase in weight per unit weight of protein consumed
NPU of cow - milk is 81%
NPU of average Indian foods is 50 - 80%
If NPU is low, more protein is required