Answer:
D.
Step-by-step explanation:
First, multiply straight across and put everything together:
[tex]\frac{3a}{b}\cdot \frac{b^2}{12c}=\frac{3ab^2}{12cb}[/tex]
Notice we can simplify by cancelling a b and reducing 3/12:
[tex]=\frac{ab}{4c}[/tex]
This cannot be simplified further.
D.
