Any set of boolean operators that is sufficient to represent all boolean expressions is said to be complete. Which of the following is not complete?
(A) {NOT, OR}
(B) {NOR}
(C) {AND, OR}
(D) {AND, NOT}


Answer: (C)

Explanation: NOR and NAND are the universal gates as any logic gate can be implemented using these two logic gates.
i) {NOT, OR}
Combining these two gates make NOR gate only which itself is a universal gate.
iii) {AND, OR}
These two gates do not make a universal gate.
iv) {AND, NOT}
Combining these two gates make NAND gate which is again a universal gate.
So, option (C) is correct.

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