Ans: (b) IInd trimester (at 20 week) ✔

Explanation:
(a) First trimester:
During the first trimester (up to approximately 13 weeks gestation), the fetus is still very small and deeply positioned within the pelvis. Fetal parts are not typically palpable externally during this early stage of pregnancy.

(b) IInd trimester (at 20 week):
The second trimester, specifically around 20 weeks gestation, marks a significant milestone when fetal parts become palpable. By this time, the fetus has grown larger and its limbs and body parts have developed enough to be felt through the mother’s abdominal wall.

(c) Third trimester:
In the third trimester (approximately after 28 weeks gestation), the fetus continues to grow and develop, becoming more easily palpable. By this stage, fetal movements are also more pronounced and can be felt by the mother.

(d) Just after conception:
Immediately after conception, the fertilized egg (zygote) begins to undergo rapid cell division and travels down the fallopian tube to implant in the uterus. At this very early stage, the embryo is microscopic and not palpable externally. Palpation of fetal parts becomes possible only much later in pregnancy as the fetus grows and develops.

In summary, the correct answer remains (b) IInd trimester (at 20 week) as this is the typical timeframe when fetal parts can first be palpated during a pregnancy.