When two objects of different masses, different temperatures, and different sizes are placed in thermal contact, energy will always travel a. from the hotter object to the cooler object b. from the bigger object to the smaller object c. from the more massive object to the one with less mass

a) from the hotter object to the cooler object

Explanation:

temperature moves by conduction,  which is associated with the movement of  atoms or molecules and the always move from hight temperatures to lower temperatures to attain thermal equilinrium of the system.

so when two objects are placed together and have different temperatures then the system is not in thermal equilibrium and to attain it, temperature can only move to coller object and not from the coller object according to thermodynamics.