Answer:
b. electroscope.
Step-by-step explanation:
-A magnet is an object that creates a magnetic field around it and has two poles.
-An electroscope is an instrument that helps to find out if there is a charge in an object.
-A generator is an object that produces electrical energy.
-A conductor is an object that allows to transmit energy.
According to this, the answer is that an instrument that can detect the presence of an electric charge is an electroscope.