What is an increase in the size of the cell following cell injury known as?

The correct answer is b).

• Hypertrophy refers to an increase in the size of individual cells, which leads to an increase in the size of the organ or tissue. This can occur in response to increased workload or injury.
• Atrophy is the decrease in cell size.
• Hyperplasia is an increase in the number of cells.
• Metaplasia is a reversible change where one mature cell type is replaced by another mature cell type.

Therefore, an increase in the size of the cell following cell injury is known as hypertrophy.

The final answer is $\boxed{\text{b. Hypertrophy}}$.