Additive synthesis is a sound generating module that combines waves in a variety of amplitudes, frequencies, and phases. Excellent!
Additive synthesis is a sound generating technique that combines a rich sound sound and one or more filters to create a new color. This is the definition of subtractive synthesis.
Additive synthesis is a sound generating module that can play back samples. This is the defintion of a sampler.
Additive synthesis is a sound generating module that reduces rich sound waves in a variety of amplitudes. This answer doesn't make sense.