Simply by observing the existence of the Cherenkov radiation from a particle, one can determine its relative velocity with respect to the light speed in medium. Knowing that, one can determine the particle momentum.
It is a ring formed carbon skeleton. The smallest possible cyclic hydrocarbon is cyclopropane (triangular C3H6) together with cyclobutane both being rather unstable (degration to linear propene and 1-butene). Five and six membered rings are quite common.
Because of its chemical formula, C6H6, benzene is classified as a hydrocarbon, which is a compound that consists of only carbon and hydrogen atoms. Its structure and formula reveal benzene to be an aromatic hydrocarbon, which is defined as a compound that is composed of hydrogen and carbon that has alternating double bonds forming a ring.