An academic definition has three compulsory components (1) a term to be defined; (2) the general class that the target term belongs to; (3) the differentiating features of the target term. Please identify to which categories the underlined part is in the following definition.The metabolic rate of an animal is a measure of the overall energy needs that must be met by the animal ingestion and digestion of food.
选项：

A:A term to be defined;;
B:The general class that the target term belongs to;;
C:Differentiating features of the target term;;
D:/