The correct answer is: B. Promisor need not perform his part of promise unless promise is ready and willing to perform his reciprocal promise.
This is because of the doctrine of mutuality of obligation. This doctrine states that for a contract to be valid, each party must be obligated to perform their promise. If one party is not obligated to perform their promise, then the contract is not valid.
In the case where a contract consists of reciprocal promises and such reciprocal promises are to be simultaneously performed, each party is obligated to perform their promise at the same time. This means that the promisor cannot be required to perform their part of the promise unless the promisee is ready and willing to perform their reciprocal promise.
Option A is incorrect because the promisor does need to perform their part of the promise, but only if the promisee is ready and willing to perform their reciprocal promise.
Option C is incorrect because the promisor cannot compel the promisee to perform their promise. The promisor can only sue the promisee for breach of contract if the promisee does not perform their promise.
Option D is incorrect because a contract can be valid even if the reciprocal promises are to be simultaneously performed. The only requirement is that each party is obligated to perform their promise.