Answer:
Interchangeable is something that can be used in the same manner as something else without any important differences.
or in a more simple way
something that can be exchange
For example when two sweaters look almost the same and you could easily wear either one with a particular skirt, this is an example of when the sweaters can be worn interchangeably.
I believe the answer is the second one.
Current= voltage divided by resistance
120/30=4
I believe it’s B. Electrons