Final answer:
The process in which adipocytes fill with lipid and increase in size is known as hypertrophy.
Step-by-step explanation:
The process of an adipocyte filling with lipid and increasing its cell size is called hypertrophy. Adipocytes are specialized cells for lipid storage and are a crucial component of adipose tissue. This process of hypertrophy is observed when white adipocytes, which store lipids as a single large drop, expand to store larger amounts of fat, a condition often observed in obese individuals.
Unlike hypertrophy, which refers to the increase in cell size, hyperplasia is the process by which cell numbers increase due to cell division, and cellular equilibrium suggests a balance in cell size and number. Therefore, the correct answer to the question is a. hypertrophy.