Frogs differ from humans in possessing

In a frog, the vertebra with an anterior convex surface is:

$A$ hibernating frog respires with

In frogs, the alimentary canal opens into which of the following at the end?

Select the correct option regarding the respiratory system of a frog:
$(1)$ The glottis is covered by a thin,elastic cartilaginous flap called the epiglottis.
$(2)$ Frogs respire through gills or moist skin.

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