The Boolean expression for NAND gate is -
A
$$Y = \overline {A + B}$$
Correct option is D. $$Y = \overline {A. B}$$
The Boolean algebra for $${\text{AND}}$$ gate is-
$$Y = A.B$$
So, the Boolean algebra for $${\text{NAND}}$$ gate is-
$$Y = \overline {A.B} $$