Answer:
D
Explanation:
The equation of an exponential function is
y = a

To find a and b, substitute (1, 12) and (2, 36) into the equation
(1, 12) → 12 = ab → (1)
(2, 36) → 36 = ab² → (2)
divide (2) by (1)
=

b = 3
substitute b = 3 into (1)
12 = 3a ⇒ a = 4
f(x) = 4
→ D