Assertion (A): The placental barrier prevents the mixing of mother's blood with the fetal blood.
Reason (R): During implantation, placenta is developed from the embryonic membrane called chorion.

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

To analyze the assertion and reason provided in the question, we can break down the solution into the following steps:

### Step-by-Step Solution:

1. **Understanding the Assertion (A)**:
- The assertion states that "The placental barrier prevents the mixing of mother's blood with the fetal blood." This is true as the placenta acts as a selective barrier that allows nutrients and gases to pass between the mother and fetus while preventing the direct mixing of their blood.

2. **Understanding the Reason (R)**:
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