Question

A system X is neither in thermal equilibrium with Y, nor with Z. The systems Y and Z thermal equilibrium.

• A. must be in
• B. must not be in
• C. may be in

Answer 1

The correct option is C may be in

Let the temperatures of X, Y and Z be T_x, T_y and T_z, respectively.
Given, T_x ≠ T_y,
and T_x ≠ T_z.

This does not tell us anything about T_y and T_z, except that they are not equal to T_x.
So, T_y = T_z, and T_y ≠ T_z, both are possibilities!
So they can be in thermal equilibrium.