Assertion :Catalyst can increase that rate constant to a large extent.
Reason :By using suitable catalyst, we can significantly increase yield.

A catalyst increases the rate of reaction either by increasing A or by-decreasing $E_a$ or by doing both. Though catalyst is involved in the reaction, it does not appear in the over all reaction. Thus,its concentration remains constant throughout the chemical reaction.Also it has no effect on yield as it doesnt affect product formation.