is the enlargement of muscle fiber cross-sectional area, and is the increase in the number of muscle fibers via longitudinal fiber splitting.

The correct answer is hypertrophy and hyperplasia.

Explanation:

An enhancement and growth of muscle cells or cross-sectional enlargement of muscle fiber is termed as hypertrophy. Hypertrophy is generally achieved via exercise like weight-lifting is the most general cause of hypertrophy.  

On the other hand, an increase in the number of muscle fibers due to cell proliferation or longitudinal fiber dissociation is termed as hyperplasia. The term hyperplasia at certain times is also associated with a benign tumor or neoplasia. An increase in the number of cells is hyperplasia and an increase in the size of cells is hypertrophy.