Assertion (A): Allantois finally converts to the umbilical cord.
Reason (R): Umbilical cord helps in mixing of body fluids of the mother and the foetus.

Options

A. Both A and R are true and R is the correct explanation for A.
B. Both A and Rare true, but R is not the correct explanation for A.
C. A is true and R is false.
D. A is false and R is true.

Explanation

### Step-by-Step Solution:

1. **Understanding the Assertion (A)**: The assertion states that "Allantois finally converts to the umbilical cord."
- The allantois is an embryonic structure that plays a role in the development of the umbilical cord. It is indeed correct that the allantois contributes to the formation of the umbilical cord.

2. **Understanding the Reason (R)**: The reason states that "Umbilical cord helps in mixing of body fluids of the mother and the foetus."
- This statement is incorrect. The umbilical cord does not mix the body fluids of the mother and fetus; rather, it serves as a conduit for nutrients and waste exchange between the mother and the fetus without mixing their blood.

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