Two J-K flip-flops with their J-K inputs tied HIGH are cascaded to be used as counters. After four input clock pulses, the binary count is ________a.11b.00c.01d.10

The answer is (d) 10.

Here's the step-by-step explanation:

1. A J-K flip-flop is a type of flip-flop that can toggle between states. When both J and K inputs are HIGH (1), the flip-flop toggles its output on each clock pulse.

2. If we have two J-K flip-flops cascaded (i.e., the output of the first flip-flop is connected to the clock input of the second flip-flop), we have a 2-bit binary counter.

3. The counter starts at 00. After the first clock pulse, the first flip-flop toggles, so the count is 01.

4. After the second clock pulse, the first flip-flop toggles again, and because its output goes from 1 to 0, it triggers the second flip-flop to toggle as well. So the count is 10.

5. After the third clock pulse, the first flip-flop toggles again, so the count is 11.

6. After the fourth clock pulse, both flip-flops toggle again, so the count goes back to 00.

Therefore, after four input clock pulses, the binary count is 10.