Option 1 and 3 are obviously true. Option 4 - Up/Down counters are pretty straight forward in implementation. So it's false. Option 3 is true because In synchronous counters, all flip-flops change simultaneously and in asynchronous counters, the propagation delay of the flip-flops add up to produce the overall delay. Although synchronous counters usually have more combinational logic, the propagation delay through these gates are small compared to the propagation delay through many stages of flip-flops.
So D is the answer.
