Atavistic epiphysis is a/an

Out of $X$ pairs of ribs in humans,only $Y$ pairs are true ribs. Select the option that correctly represents the values of $X$ and $Y$ and provides their explanation.

In vertebrate animals,where is $80 \%$ of the total phosphorus incorporated?

How many bones are present in the human trunk?

Identify the group of minerals associated with bones:

Find out the true and false statements.
$(A)$ Human skeleton has $206$ bones
$(B)$ There are $12$ pairs of ribs in human beings
$(C)$ Sternum is present on the dorsal side of the body
$(D)$ All mammals (except a few) have $8$ cervical vertebrae
$(E)$ Ribs are bicephalic