The correct answer is: A. Very low.
A test lamp is a small, low-wattage lamp that is used to test electrical circuits. It is typically used to test for continuity, voltage, and current. Test lamps are available in a variety of wattages, but the most common wattage is 12 watts.
A test lamp should have a very low wattage because it is used to test delicate electrical circuits. If a test lamp has a high wattage, it could damage the circuit that it is being used to test.
Option B is incorrect because a low-wattage test lamp is not powerful enough to test some electrical circuits.
Option C is incorrect because a high-wattage test lamp could damage the circuit that it is being used to test.
Option D is incorrect because the wattage of a test lamp must be very low.