Step 1: Count the hydrogens on nitrogen:
The reaction needs two N-H hydrogens to be lost, so the amine must have a free $-\text{NH}_2$.
Aniline: $\text{C}_6\text{H}_5\text{NH}_2$, primary.
Isopropylamine: $(\text{CH}_3)_2\text{CHNH}_2$, primary.
Benzylamine: $\text{C}_6\text{H}_5\text{CH}_2\text{NH}_2$, primary.
N,N-dimethylaniline: $\text{C}_6\text{H}_5\text{N(CH}_3)_2$, no N-H at all.
Step 2: Result:
Only the tertiary amine fails, so only it gives no foul-smelling isocyanide.
Final Answer:
Option (B).
\[ \boxed{\text{N,N-Dimethylaniline (B)}} \]