What is classified as a building block for the human body

When using two-wire cable to feed a 240-v appliance that does not require a neutral wire, you should a. mark both ends of the white wire green. b. use the cable as is. c. use only the black wire. d. mark both ends and any exposed area of the white wire black.

Will you chech and finish these for me, because i am stumped with them.

What is special about a dc circuit ?