Pregnancy And Embryonic Development

First month (i): The heart (c) begins to form and starts beating by the end of the first month (around day 21-23). This is one of the first organs to develop.

Second month (ii): Basic structures of all major organs develop, including limbs and digits (d). By the end of the second month, the embryo has distinct fingers and toes.

Fifth month (iii): Hair on head (b) (lanugo) appears, along with other features like quickening (mother feels movement).

Sixth month (iv): Separation of eyelids (a) occurs, and the eyes may begin to open. The fetus also develops more fat and more defined features.

The correct matching is therefore: (i)-(c), (ii)-(d), (iii)-(b), (iv)-(a)

Thus, the correct option is (D) (c) (d) (b) (a).

The first movements of the fetus, known as quickening, and the appearance of hair on its head are typically observed during the 5th month of gestation.

Around the 5th month of pregnancy, the fetus's musculoskeletal system develops sufficiently for it to start making noticeable movements. This is often described as fluttering or gentle flutters felt by the mother. Additionally, hair begins to grow on the fetus's head during this time.

Therefore, the correct answer is (D) 5th month.