Foramen Magnum is situated in

The vertebra in which the centrum is absent is

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

The last two pairs of ribs are named floating ribs because

How many pairs of ribs are present in human beings (in $pairs$)?

In mammals,the zygomatic arch is formed by