Following is the structural formula and a ball-and-stick model of cholic acid, a component of human ...

(a) What is the conformation of ring A? of ring B? of ring C? of ring D?

As can be seen in the following structures, the conformations of all of the six-membered rings, that is, A, B, and
C, are all chairs. The conformation of the five-membered ring, ring D, is puckered. These conformations all
represent preferred conformations and the linkages between rings prevent chair to chair interconversion.

(b) Are the hydroxyl groups on rings A, B, and C axial or equatorial to their respective rings?

The hydroxyl group on ring A is equatorial, the hydroxyl groups on rings B and C are axial.
(c) Is the methyl group at the junction of rings A and B axial or equatorial to ring A. Is it axial or equatorial to ring B?
The methyl group at the A,B ring junction is equatorial to ring A, but axial to ring B.

(d) Is the hydrogen at the junction of rings A and B axial or equatorial to ring A? Is it axial or equatorial to ring B?

The hydrogen atom at the junction of rings A and B is axial to ring A, but equatorial to ring B.

(e) Is the methyl group at the junction of rings C and D axial or equatorial to ring C?
The methyl group at the C, D junction is axial to ring C.