Answer:
a i. The higher curve is "thick wall" and the lower curve is "thin wall".
a ii. The thicker the wall, the more time it takes to transfer the same amount of heat. Thus, the thick wall would have a less steep drop in temperature as it transferred lesser heat from the room to the surroundings and the thinner wall would have a steeper drop in temperature as it conducted more heat away from the room to the surroundings.