Duff States That Equal Masses of All Substances Have Equal $\Delta$

Duff states that equal masses of all substances have equal changes in internal energy when they have equal changes in temperature.Javan states that the change in internal energy is equal to a constant times the change in temperature for every $\Delta$ T,no matter how large or how small $\Delta$ T is,but that the constant is different for different substances.Which one,if either,is correct?

A) Neither,because the specific heat depends on the substance and may vary with temperature.
B) Neither,because a change of state may involve release or absorption of latent heat.
C) Neither because a substance may do work during a temperature change.
D) All of the statements above are correct.
E) Only statements (a) and (b) are correct.