The correct option is B not illegal
There is a difference between illegal and unlawful agreements. Illegal agreements are those consideration or object of which is not legal as well as punishable in nature for example, agreement to murder someone. On the other hand, unlawful agreement are those which are not enforceable by the law i.e performance of the agreement can be done but there is no legal recourse in the eye of law. Therefore, every illegal agreement will not be enforceable by law and therefore, will be unlawful. But not every agreement not force able by law is illegal in nature. Hence, every illegal agreement is unlawful but every unlawful agreement is not illegal.