Twins are born to a family that lives next door to you. The twins are a boy and a girl. Which of the following must be true?

Consider the following : A. The reductive division for the human female gametogenesis starts earlier than that of the male gametogenesis. B. The gap between the first meiotic division and the second meiotic division is much shorter for males compared to females. C. The first polar body is associated with the formation of the primary oocyte. D. Luteinizing Hormone (LH) surge leads to disintegration of the endometrium and onset of menstrual bleeding. Choose the correct answer from the options given below:

Match List - I with List - II. $\begin{array}{|l|l|l|l|}\hline & \text{List - I} & & \text{List - II} \\\hline \text{A}. & \text{Head} & \text{(i)} & \text{Enzymes} \\\hline \text{B.} & \text{Middle piece} & \text{(ii)} & \text{Sperm motility} \\\hline \text{C.} & \text{Acrosome} & \text{(iii)} & \text{Energy} \\\hline \text{D.} & \text{Tail} & \text{(iv)} & \text{Genetic material} \\\hline\end{array}$ Choose the correct answer from the options given below :

Find the correct statement : (A) In human pregnancy, the major organ systems are formed at the end of 12 weeks. (B) In human pregnancy the major organ systems are formed at the end of 8 weeks. (C) In human pregnancy heart is formed after one month of gestation. (D) In human pregnancy, limbs and digits develop by the end of second month. (E) In human pregnancy the appearance of hair is usually observed in the fifth month. Choose the correct answer from the options given below :

The first menstruation is called :

Given below are two statements: One is labelled as Assertion $\mathbf{A}$ and the other is labelled as Reason $\mathbf{R}$. Assertion A: During menstrual cycle, the ovulation takes place approximately on $14^{\text {th }}$ day. Reason R: Rapid secretion of LH in the middle of menstrual cycle induces rupture of Graafian follicle and thereby the release of ovum. In the light of the above statements, choose the most appropriate answer from the options given below.