To enter or leave a cell, the substance must pass through .........and its structure was explained by ....... in the year ...........

Options

A. `{:(P,Q,R),("the cell wall ","the cell theory ",1978):}`
B. `{:(P,Q,R),("the plasma membrane, ","the cell theory ",1942):}`
C. `{:(P,Q,R),("the cell wall ","the fluid mosaic model ",1975):}`
D. `{:(P,Q,R),("the plasma membrane, ","the fluid mosaic model ",1972):}`

Answer

To solve the question, we need to fill in the blanks appropriately based on the information provided in the video transcript.

1. **Identify the first blank**: The question asks what a substance must pass through to enter or leave a cell. According to the transcript, the answer is the **plasma membrane**.

2. **Identify the second blank**: The transcript mentions that the structure of the plasma membrane was explained by the **fluid mosaic model**.

3. **Identify the third blank**: The transcript states that this model was proposed by **Singer and Nicholson** in the year **1972**.

Putting it all together, the complete answer to the question is:

To enter or leave a cell, the substance must pass through **plasma membrane** and its structure was explained by **fluid mosaic model** in the year **1972**.