The correct answer is B) Each heating coil inlet temperature is identical, as each parallel-connected heating coil has its own separate supply teeing off a supply main. In a two-pipe hydronic heating system, the heating coils are connected in parallel to the supply and return mains. This means that each heating coil has its own separate supply and return lines that branch off from the main supply and return pipes. Since the heating coils are connected in parallel, the inlet temperature to each coil will be the same, as the supply main provides the same temperature water to all the parallel-connected coils. The other options are incorrect because: A) and C) describe a series-connected system, where the heating coils are connected one after another, which would result in different inlet temperatures. D) describes a parallel-connected system, but states that the inlet temperatures are different, which is not the case in a two-pipe hydronic system.