What is measured by the reaction rate? the probability that a reaction will occur the speed at which products form the time required for a reaction to go to completion

the speed at which products form

Explanation:

Rate of a reaction is defined as the speed at which a chemical reaction proceeds. It is often expressed in terms of the concentration of a reactant that is consumed in a unit time or the concentration of a product that is formed in a unit of time.

For a general reaction :

or

where d[A] = change in concentration of reactant A

d[B] = change in concentration of product B

dt = time interval

the answer is c.the valence of the atoms combine .