Question

Assertion (A) : Blastocyst becomes embeded in the endometrium of the uterus.

Reason (R) : The morula divides and transforms into blastocyst.

• 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, but the morula to blastocyst change does not explain implantation.

Answer 1

The Correct Option is B

Step 1: Check the Assertion:
After fertilisation the zygote divides to form a morula, which then becomes a blastocyst as it reaches the uterus.
The blastocyst sinks into the endometrium of the uterus. This is implantation. So (A) is true.

Step 2: Check the Reason:
The morula (8 to 16 cells) keeps dividing and forms a blastocyst, which has an outer trophoblast layer and an inner cell mass. So (R) is also true.

Step 3: Does R explain A?:
R tells how the blastocyst is formed. It does not tell why or how the blastocyst gets embedded.
Implantation happens because the trophoblast cells attach to the endometrium and the uterine wall is ready. Forming the blastocyst is only an earlier stage.
So R is true but not the explanation of A.

Final Answer:
Option (B).