Abiologist adds a vitamin solution, which acts as a co-factor, to an enzyme/substrate solution. what affect will this have on the enzymes in the solution?

it will increase the reactivity with the substrates.
it will decrease the reactivity with the substrates.
it will inhibit bonding between the enzyme and vitamins.
it will stimulate bonding between the enzyme and vitamins.

is it a or b? someone me you!