If a new contract is substituted in place of an existing contract, it is called:

Correct option is C

Novation occurs when a new contract replaces an existing contract with the agreement of all parties involved. This means that obligations under the old contract are completely discharged, and a fresh contract with new terms takes effect.
Incorrect options:
· Waiver (a): This refers to the voluntary relinquishment of a legal right.
· Remission (b): This involves accepting a lesser amount than what is due.
· Alteration (d): This means modifying the terms of an existing contract without replacing it entirely.