A fish which produces electric current is
A) Trygon
B) Torpedo
C) Pristis
D) All of the above

Hint: Electric fish is a fish which generates electric fields. They are found both in the ocean and freshwater. The fishes that can generate electric fields are called electrogenic fishes.

Complete answer
To answer this question, we must know about the electrogenic fishes.
There are two types of fishes depending on the response to electric fields. Electrogenic fishes are the fishes which can produce electric fields whereas electroreceptive fishes have the ability to detect electric fields. Most electrogenic fishes are electroreceptive. Electric fishes produce electric fields by a specialised structure called electric organ. This organ is made up of nerve cells which are capable of producing stronger bioelectric fields. The organ is located in the tail of the electric fish. The electric organ discharges powerful electric current which is used in defence. For example electric eel, electric catfishes, electric rays.
Torpedo is an electric ray. It is a cartilaginous fish. These are capable of producing electric discharge ranging from 8 to 220 volts. They use electric discharge to stun prey and for defence. Thus these fishes are electrogenic in nature.
Trygon is commonly called stingray but does not have an electric organ.
 Pristis are called saw fishes. They cannot produce electric discharge.
 They both can detect the electric field but cannot produce it. Thus are called electroreceptive fishes.

Thus the correct answer is (B) Torpedo is an electric fish.

Note: Electric fishes use electric discharge to stun their prey and in defence. Electric fishes are electrogenic fishes. Many fishes are electroreceptive. They can only sense the electric field.