Final answer:
The process where a child gains weight and height is called growth, the increase in body size, which happens most rapidly during infancy and adolescence.
Step-by-step explanation:
The process by which a child gains weight and becomes taller each year is called growth. Growth is the increase in body size and involves not just an increase in the number of cells but also an increase in non-cellular material such as mineral deposits in bones, and a sometimes slight increase in the size of existing cells. This process is part of a broader category known as development, which includes not only physical growth but also differentiation in which cells become specialized and functions such as repair. Growth is most rapid during infancy and adolescence when numerous physical, cognitive, and social changes occur.
Answering the original question, the correct option is D) Growth.