Answer - D. Both B & C
A two input NOR gate is equivalent to both Bubbled AND gate & negative AND gate.
A two-input NOR gate produces an output, which is the complement of logical OR among the two input variables. Mathematically, it is represented as Y=(A+B)'.
By using De-Morgan’s law, we can write (A+B)'=A'. B'
For implementing the above expression, we require two NOT gates & a two-input AND gate. The circuit diagram for realizing the expression Y is shown below.
We can reduce the above circuit to a two-input AND gate, which has bubbles at the input. It is known as the Bubbled AND gate. This logic symbol is shown in the figure below.
The normal AND gate produce an output, which is the logical AND among the input variables. Whereas the bubbled AND gate produces an output, which is the logical AND among the complemented inputs. Hence, it is also known as the Negative-AND gate. Hence, Option (D) is the correct answer.