Conceptually, this seems to be buoyancy vs density and PV=nRT. Since n, R, and P are held constant, as temperature goes up, Volume must go up as well. Think of what happens to a water bottle left in a hot car. It expands and appears bloated.
Remember, buoyancy is a function of volume displaced and relative densities between the object and the surrounding medium. The greater the density difference, the greater the buoyant force. So a balloon filled with a lower density gas will rise faster than a higher density gas.
Given the same object weight, the more volume that is displaced, the more buoyant force pushing upwards. Referring back to PVnRT, as the temp goes up, so does the volume of the balloon. Since the volume goes up, the volume displaced goes up, and the buoyant force goes up.
To combine these two concepts, the balloon with a less dense gas and a higher temp will rise the fastest. Thus this is Balloon B at 100C.
Note I didn’t do any calculations! Sometimes you don’t actually have to. Saves you time and energy.
