Which one of the following list contains only the mesodermal structures

$A$ : If both the ovaries are removed after the first trimester of pregnancy, still there would be normal growth of foetus.
$R$ : After first trimester placenta secretes sufficient progesterone

The female rabbit is

In vertebrates the central nervous system devlops under the influence of

A woman with a typical $28 \;day$ menstrual cycle is most likely to become pregnant as a result of sexual intercourse on ….. of cycle