When comparing the two chair conformations for a monosubstituted cyclohexane ring, which type of substituent shows the greatest preference for occupying an equatorial position rather than an axial position?

A. Polar substituents
B. Large substituents
C. Substituents with lone pairs
D. Small substituents

Large substituents will chose equatorial conformation over axial conformation more readily.

The axial conformation of the monosubstituted cyclohexane molecule is the Conformation where the substituted group is located along the axis of the molecule, perpendicular to the plane of the molecule. The equatorial conformation on the other hand is the substituted group being aligned along the plane of the molecule.

Now, in the axial position, the large groups will face steric hindrance with the axial hydrogens of the other carbon atoms which will lead the molecule more unstable. So larger is the group, more is the steric hindrance. So larger group will prefer the equatorial conformation more readily than the axial conformation.

the answer is definitely c.