What are the four main parts of an EDFA?

What are the four main parts of an EDFA?

A.
Isolator, coupler, splitter, and pump

B.
Isolator, splitter, pump, and filter

C.
Coupler, splitter, pump, and doped fiber

D.
Isolator, coupler, pump, and doped fiber

E.
Coupler, pump, doped fiber, AWG