Question

If heat is supplied to a solid, its temperature

(a) must increase
(b) may increase
(c) may remain constant
(d) may decrease

Answer 1

(b) may increase
(c) may remain constant

When heat is supplied to a solid, it is used up either to increase the temperature of the body or to change its state from one form to another by breaking the bonds between the molecules (without raising the temperature).
When heat is supplied to the solid, the internal energy of the solid increases, so the temperature does not decrease.