Frogs reproduce in . . . . . . .

Which vein drains blood from the back region in a frog?

Consider the following four statements $(A-D)$ related to the common frog $Rana$ $tigrina$, and select the correct option stating which ones are true $(T)$ and which ones are false $(F)$.
Statements:
$A.$ On dry land, it would die due to lack of $O_2$ if its mouth is forcibly kept closed for a few days.
$B.$ It has a four-chambered heart.
$C.$ On dry land, it turns uricotelic from ureotelic.
$D.$ Its life-history is carried out in pond water.

In frog, a triangular structure called $A$ joins the $B$:

Identify $X, Y$ and $Z$ in the given figure of the female reproductive system of a frog.

How does a frog differ from a human in terms of blood characteristics?