Why do elements need to be heated to emit color?

The combining of light nuclei is called blank. blank as in not actually blank. you know what im tryin to say.

The receptor cells that convert light energy into neural signals are called

Arock displaces 1.65 l of water. the volume of the rock is: a: 1,650 cm³ b: 165.0 cm³ c: 16.50 cm³ d: 0.165 cm³