A agrees to pay 'B' a sum of money, if 'B' marries 'C'. 'C' marries 'D'. The agreement is:

Solution (By Examveda Team)

First, let's define the relevant legal terms:
Void Agreement: An agreement that is not enforceable by law. It lacks the essential elements of a valid contract, such as free consent or lawful consideration.
Voidable Agreement: An agreement that is valid until one of the parties chooses to set it aside. It is enforceable unless it's avoided by the aggrieved party.
Legal Agreement: An agreement that is valid and enforceable by law. It fulfills all the necessary requirements for a legally binding contract.
Illegal Agreement: An agreement that is prohibited by law. Such agreements are void and unenforceable.

Now, let's analyze the given scenario. A promises to pay B a sum of money if B marries C. However, C marries D, making B's marriage to C impossible.

The agreement between A and B becomes impossible to perform because the condition precedent (B marrying C) cannot be fulfilled. A condition precedent is a condition that must be satisfied before a contract becomes effective. If the condition precedent becomes impossible, the contract becomes void, not merely voidable. The impossibility is not due to any fault of either party, but rather due to the intervention of a third party (C marrying D).

Therefore, the correct answer is Option A: Void.

The other options are incorrect because:
Option B: Voidable is incorrect because there's no element of fraud, misrepresentation, undue influence, coercion or mistake that would make it voidable at the option of B. The contract is inherently incapable of performance.
Option C: Legal is incorrect as the agreement becomes impossible to perform due to the supervening impossibility of the condition precedent.
Option D: Illegal is incorrect because there's nothing inherently unlawful in the agreement itself. The agreement becomes void due to impossibility, not illegality.