**Question:** Fertilization takes place after how much time of ovulation -

A. 24 hours
B. 36 hours
C. 48 hours
D. 72 hours

**Core Concept:** Ovulation is the release of an egg from the ovary, typically occurring around the 14th day of a 28-day menstrual cycle in a woman with regular menstrual cycles. Fertilization occurs when sperm meets the released egg (ovum) in the fallopian tube.

**Why the Correct Answer is Right:** Fertilization typically occurs 24 hours after ovulation, when sperm can penetrate the egg and fertilization occurs. This is known as the "ovulation window" and is critical for successful reproduction.

**Why Each Wrong Option is Incorrect:**

A. 24 hours is too short, as it assumes immediate fertilization, but sperm survival is limited to around 5 days.
B. 36 hours is too long, as it assumes immediate fertilization, but sperm survival is limited to around 5 days.
C. 48 hours is too long, as sperm survival is limited to around 5 days, and fertilization may not occur immediately after ovulation.
D. 72 hours is too long, as sperm survival is limited to around 5 days, and fertilization may not occur immediately after ovulation.

**Clinical Pearl:** Understanding the timing of ovulation and fertilization is crucial for fertility treatments and predicting the optimal time for intercourse to increase the chances of conception.

**Correct Answer Explanation:** The correct answer is A, as it acknowledges the limited sperm survival and the potential delay in fertilization occurring 24 hours after ovulation. This ensures that students understand the importance of timing and the limited lifespan of sperm and the egg.