What Should Be Done to Unused Inputs on TTL Gates

Multiple Choice

What should be done to unused inputs on TTL gates?

A) All unused inputs should be connected to an unused output; this will insure compatible loading on both the unused inputs and unused outputs.
B) All unused gates should be connected together and tied to Vcc through a 1k- ohm resistor.
C) They should be left disconnected so as not to produce a load on any of the other circuits and to minimize power loading on the voltage source.
D) Unused AND and NAND inputs should be tied to Vcc through a 1k- ohm resistor; unused OR and NOR inputs should be grounded.