The correct answer is (a). Contingent interest.
A contingent interest is an interest in property that is not certain to vest. In this case, C’s interest in the property is contingent on him attaining the age of majority. If C does not attain the age of majority, his interest in the property will lapse and the property will revert to A.
A vested interest is an interest in property that is certain to vest. In this case, A has a vested interest in the property because he is the current owner of the property.
Both contingent and vested interest is not the correct answer because C does not have a vested interest in the property.
No interest is not the correct answer because C does have an interest in the property, even though it is a contingent interest.