An electric current that is varied to represent information is a(n)
a. electronic signal.
b. digital signal.
c. integrated circuit.
d. electromagnetic wave.

a).  You'd have to call that simply an electronic signal.

b).  Although most signals nowadays carry the information
in digital form, they don't absolutely NEED to.

c).  An integrated circuit is one of the "chips" in an electronic device
that make the device work.

d).  An electromagnetic wave is a wave of radio, infrared, visible light,
ultraviolet, X-ray, gamma ray, etc.