Correct Answer: Lumen

Solution : The first option is the correct answer.

Lumen is a unit used to measure the total quantity of visible light emitted by a source per unit of time.

The meanings of the other options are as follows:

• The watt is the unit of power in the International System of Units (SI).
• Horse power is a unit of power used in the context of mechanical power.
• The ampere is the unit of electric current in the International System of Units (SI).

Therefore, the correct answer is lumen.