Which one of the following generates new genetic combinations leading to variation?

$A-$ Events after the formation of zygote are called post fertilization events

$R -$ In viviparous animals a young one develops out side the mother body

Which of the following plants is monoecious ?

Formation of a sporophyte from gametophyte and vice versa is termed as

Which of the following statements are correct regarding female reproductive cycle?

$A$. In non-primate mammals cyclical changes during reproduction are called oestrus cycle.

$B$. First menstrual cycle begins at puberty and is called menopause.

$C$. Lack of menstruation may be indicative of pregnancy.

$D$. Cyclic menstruation extends between menarche and menopause.

Choose the most appropriate answer from the options given below.