The correct answer is (a). The choke in a tubelight is a coil of wire that is used to limit the current flowing through the tube. This is necessary because the tube would otherwise draw too much current and overheat. The choke does this by creating a magnetic field that opposes the flow of current. This magnetic field creates a voltage drop across the choke, which reduces the amount of current that flows through the tube.
Option (b) is incorrect because the choke actually decreases the current. Option (c) is incorrect because the choke does not decrease the voltage momentarily. Option (d) is incorrect because the choke does not increase the voltage momentarily.