The combination of many sine waves with different frequencies, amplitudes, and phases, all of which change over time. Correct!
The surrounding of many inharmonic waves around a single area. Formants do give the sound some color, but some sounds don't have formants.
The combination of many sine waves with different frequencies, amplitudes, and spectrums, all of which change over time. Sine waves do not have unique spectrums, individually.
The combination of many sine waves with different frequencies, all of which change over time. This is partially true...