Human cells in culture show a cell cycle to be completed in approximately.

Options

A. 42 hours
B. 24 hours
C. 24 minutes
D. 24 seconds.

Explanation

To solve the question regarding the duration of the cell cycle in human cells cultured in vitro, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the Cell Cycle**: The cell cycle consists of several phases, including interphase (which has G1, S, and G2 phases) and the mitotic phase (which includes mitosis and cytokinesis).

2. **Duration of Interphase**: Most adult mammalian cells spend a significant portion of their time in interphase. This phase accounts for approximately 90-96% of the total cell cycle duration.

3. **Average Duration**: For human cells in culture, the average time taken to complete the entire cell cycle is approximately 24 hours. This includes all phases of interphase and the mitotic phase.

4. **Identifying the Correct Option**: The options provided were 42 hours, 24 hours, 24 minutes, or 24 seconds. Based on the information that human cells complete their cell cycle in about 24 hours, we can conclude that the correct answer is 24 hours.

5. **Final Answer**: Therefore, the human cells in culture show a cell cycle to be completed in approximately **24 hours**.