Step 1: What is discharge?
Under the Negotiable Instruments Act, a party is discharged when his liability on the instrument ceases (payment, cancellation, release, or operation of law). This supports (a).
Step 2: Specific instance.
If the holder releases or discharges the maker/acceptor, the maker’s liability ends — (c) is also correct.
Step 3: Why (b) is wrong.
Endorsement transfers title but the endorser generally remains secondarily liable to subsequent holders unless discharged.
\[
\boxed{(d)}
\]