Coal rank is a measure of coal maturity and is the most fundamental parameter that relates both to the coalification history and the utilisation potential of a coal. As the rank increases, the vitrinite reflectance, carbon content, and C/H ratio of coal increase, while the coal volatile matter decreases.
I put a circle over the arrow. hope this helps.
An amino acid is a type of organic acid that contains a carboxyl functional group (-COOH) and an amine functional group (-NH2<span>) as well as a side chain (designated as R) that is specific to the individual amino acid. </span>
Polar molecules i believe