What does c equal??

PLEASE SOMEONE HELP

Transportation is the largest single source of air pollution in the united states. air pollution can harm the environment and human health. which technology could offer a solution to this problem? mufflers that reduce noise motors that run on electricity tires that improve gas mileage

How many lone pairs of electrons are on the central atom of no3- and what is the molecular shape? one, trigonal planar zero, trigonal pyramidal zero, trigonal planar one, tetrahedral one, trigonal pyramidal

Two like-charged particles are placed close to each other. how would the force of repulsion be affected if the charge on one of the particles is doubled and that on the other is reduced to half the original value?