**Core Concept**
Hyperplasia and hypertrophy are two distinct types of cellular responses to increased demand or stress. Hyperplasia involves an increase in the number of cells, whereas hypertrophy involves an increase in the size of individual cells.

**Why the Correct Answer is Right**
The correct answer is a condition where both hyperplasia and hypertrophy occur simultaneously, leading to an increase in both cell number and size. This phenomenon is often seen in conditions where there is a significant increase in workload or demand, such as in the heart muscle during exercise or in the liver during pregnancy. The increased workload triggers an adaptive response that involves both an increase in cell number (hyperplasia) and an increase in cell size (hypertrophy).

**Why Each Wrong Option is Incorrect**
**Option A:** is incorrect because it does not accurately describe a condition where both hyperplasia and hypertrophy occur.
**Option B:** is incorrect because it is a condition that is primarily characterized by atrophy, which is the opposite of hypertrophy.

**Clinical Pearl / High-Yield Fact**
In conditions where there is a significant increase in workload, the adaptive response involves both hyperplasia and hypertrophy. This is a key concept to remember in understanding how tissues adapt to increased demand.

**Correct Answer: C.** Cardiac muscle during exercise.