Answer:
The correct answer would be "to regulate cell reactions".
Lactase is an enzyme that catalyzes the hydrolyses of lactose to form glucose and galactose.
It is present in the small intestine of mammals including humans and help in digestion of milk sugar that is, lactose.
The overall reaction can be written as:
C₁₂H₂₂O₁₁ (lactose) + H₂O → C₆H₁₂O₆ (glucose) + C₆H₁₂O₆ (galactose)+ heat