The correct option is that when a bill is referred to a joint sitting of both Houses of Parliament, it must be passed by a simple majority of the members present and voting. This requirement reflects the procedural framework established by Article 108 of the Indian Constitution, which facilitates consensus and expedites the legislative process. By allowing passage based on a simple majority, the joint sitting can effectively reconcile differing viewpoints of the Lok Sabha and Rajya Sabha, ensuring that legislative action is not stalled, thereby upholding the principle of parliamentary democracy.