Why all Digital Electronics Circuits use DC and Not AC?

The question will be little confusing.
But the answer is simple.



AC Vs DC



In Digital Electronics, Gates are the basic Elements.
Actually this Gates are made up of Transistors.



NAND gate using Transistors



Transistors are working as a Switch in Digital Electronics.



Transistor as a Switch



ie, When control signal is present, Transistor is ON, otherwise Transistor is OFF.

Now, What