Step 1: Track carbons
CH3Br has one carbon and CN adds one more, so A has two carbons and B must also have two carbons.
Step 2: Track the functional group
The CN group ($\text{C}\equiv\text{N}$) is reduced to $\text{CH}_2\text{NH}_2$ with Na/ethanol.
Step 3: Product
$\text{CH}_3\text{CN} \to \text{CH}_3\text{CH}_2\text{NH}_2$, ethanamine.
Step 4: Answer
Option (B). Methanol has one carbon and no nitrogen, ethanol has no nitrogen and ethane has no nitrogen, so none can come from a nitrile reduction.
Final Answer:
B is ethanamine. This is option (B).
\[ \boxed{\text{(B) }\text{Ethanamine}} \]