The modern unit of intensity of light is:

The correct option is C

lux

Explanation for correct option:

1. The modern unit of intensity of light is lux.
2. Lux is one of the units for the measurements of light, it describes how much light falls on a certain area.

Explanation for incorrect options:

1. Watt is a unit of power.
2. Foot-candle is an old unit of measurement of light intensity.

Hence, the correct answer is option (C).