The correct option is A Essential
An essential amino acids is an amino acid that cannot be synthesised by the organism being considered, a therefore must be supplied in its diet.
The ten amino acids human cannot synthesize are phenylalanine, threonine, tryptophan, methionine, leucine, isoleucine, lysine, valine, arginine and histidine. So leucine is an essential amino acid for protein synthesis, Additionally, similarly to other amino acids, the skeleton of leucine canbe used to generate ATP. Hence the correct answer is option a.