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.01b.00c.10d.11

The answer is c.10.

Here's the step by step explanation:

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

2. In this case, two J-K flip-flops are cascaded, meaning the output of the first flip-flop is connected to the clock input of the second flip-flop. This configuration is often used to create counters.

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 changes 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 would be 00.

However, the question asks for the count after four input clock pulses, which would be the state before the fourth pulse has an effect. Therefore, the count is 10.