Which of these would NOT produce visible light? A) flint B) lightning C) microwave D) sun

A microwave

Explanation

The human retina can only detect incident light that falls in waves 400 to 720 nanometers long, so we can't see microwave or ultraviolet wavelengths. This also applies to infrared lights which has wavelengths longer than visible and shorter than microwaves, thus being invisible to the human eye.

C.) Microwave

Explanation:

USAtestprep

i think the answer would be reserve.