Solution

The correct answer is A - II, B - I, C - IV, D - III

Key Points

• N-bit Ring Counter:
  • This type of counter circulates a single '1' or '0' bit around a ring of N flip-flops. It counts exactly N states. So, A matches with II.
• Synchronous Counter:
  • In this counter, all flip-flops are driven by a common clock signal. It uses a universal clock for all flip-flops. So, B matches with I.
• Asynchronous Counter:
  • In this counter, the flip-flops do not change states at exactly the same time because they do not share a common clock signal. The main clock is applied to the first flip-flop only. So, C matches with IV.
• Decimal Counter:
  • This counter counts from 0 to 9 and then resets to 0. It is also known as a decade counter. So, D matches with III.

Therefore, the correct option is A - II, B - I, C - IV, D - III. So, the correct option is 3).