Ingredients and their sources

The plant products used as ingredients for making tea are

Ingredients of a atmosphere present in minute quantities but essential for maintaining life on earth are

A source of sound gives 5 beats when sounded with another source of frequency 100 Hz. The second harmonic of the source together with a source of frequency 200 Hz gives 10 beats s^(-1) . What is the frequency of the source?

_________ is used as an ingredient in mouth washes.