Acatalyst -
a. causes a reaction.
b. increases a reaction's rate.
c. has no effect on a reaction.
d. raises the temperature for a reaction.

in chemistry, a solution’s concentration is how much of a dissolvable substance, known as a solute, is mixed with another substance, called the solvent. the standard formula is c = m/v, where c is the concentration, m is the mass of the solute dissolved, and v is the total volume

let that person have a turn to speak : )