20.
The answer is: D
Explanation
The correct option is D: Sec. 56.
Frustration of contract is provided by Section 56 of the Indian Contract Act, 1872. This section states that a contract becomes void when it becomes impossible or unlawful to perform due to some unforeseen event that was not in the contemplation of the parties at the time of entering into the contract. The event must be such that it affects the very foundation or essence of the contract and makes the performance radically different from what was agreed upon. The doctrine of frustration is based on the principle of justice and fairness, and it relieves the parties from their obligations when the performance becomes impossible or impracticable due to no fault of their own. You can read more about the doctrine of frustration and its application in various cases from the web search results I have provided.