0 to 6 Counter
A 0 to 6 counter is a type of counter circuit that can count from 0 to 6. It consists of three flip-flops and a combination circuit. The flip-flops are used to store the binary value of the count, while the combination circuit is used to generate the next count based on the current count.

Combination Circuit
The combination circuit in the 0 to 6 counter is responsible for generating the next count based on the current count stored in the flip-flops. It consists of two input gates, which are used to perform logical operations on the inputs.

Options
Let's go through the given options one by one to determine the correct combination circuit for the 0 to 6 counter.

Option A: One AND Gate
If the combination circuit consisted of only one AND gate, it would not be able to generate the next count based on the current count stored in the flip-flops. An AND gate can only output a high signal (logic 1) when all of its inputs are high. Therefore, it cannot be used to generate the desired count sequence.

Option B: One OR Gate
Similarly, if the combination circuit consisted of only one OR gate, it would not be able to generate the next count based on the current count stored in the flip-flops. An OR gate can output a high signal (logic 1) when any of its inputs are high. This would not allow for the desired count sequence.

Option C: One AND Gate and One OR Gate
If the combination circuit consisted of one AND gate and one OR gate, it would be possible to generate the next count based on the current count stored in the flip-flops. The AND gate can be used to check specific input conditions, and the OR gate can be used to combine the outputs of the AND gate and the flip-flops to generate the next count.

Option D: Two AND Gates
The correct answer is option D, which states that the combination circuit consists of two AND gates. With two AND gates, it is possible to perform more complex logical operations on the inputs. By using two AND gates, it is possible to generate the desired count sequence based on the current count stored in the flip-flops.

In conclusion, option D is the correct answer because it states that the combination circuit in the 0 to 6 counter consists of two AND gates, which allows for the generation of the next count based on the current count stored in the flip-flops.

Counter must be reset when it counts 111. This can be implemented by the following circuitry