Question

Which one of the following letters is used as an abbreviation when representing a unit of electric

current?
A. C
B. A
C. R
D. E

Answer 1

A.C: It is the abbreviation of Alternating Current 

Answer 2

You have several electrical units listed there:

a). C often used to represent a Capacitance.

b). 'A' often represents 'Ampere', the unit of Current.

c). 'R' often used to represent a Resistance.

d). 'E' often used to represent a Voltage (Electromotive Force).

Not to mention ' A. C ', a whimsical offering,
reminiscent of 'Alternating Current'.