Question

Assertion (A) : After implantation, finger-like projections appear on the trophoblast called chorionic villi.

Reason (R) : Chorionic villi are surrounded by the uterine tissue and the maternal blood.

• A. Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of the Assertion (A).
• B. Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of the Assertion (A).
• C. Assertion (A) is true, but Reason (R) is false.
• D. Assertion (A) is false, but Reason (R) is true.

Hint:

Both statements are true facts about chorionic villi, but the surroundings do not explain how the villi form.

Answer 1

The Correct Option is B

Step 1: Check the Assertion:
After the blastocyst implants in the endometrium, the trophoblast grows finger-like projections. These are called chorionic villi.
So the Assertion (A) is true.

Step 2: Check the Reason:
NCERT says the chorionic villi are surrounded by the uterine tissue and the maternal blood. So the Reason (R) is also true.

Step 3: Decide if R explains A:
The Assertion tells us how the villi form on the trophoblast. The Reason tells us what lies around them.
The surroundings do not cause the villi to appear. So R does not explain A.

Step 4: Check the codes:
Option (A) needs R to explain A, which is not so. Option (B) says both are true but R is not the explanation, which fits. Options (C) and (D) say one statement is false, which is not so.

Final Answer:
Both statements are true, but R is not the explanation of A. This is option (B). \[ \boxed{\text{(B)}} \]