The correct answer is option 1: casting vote. In the Lok Sabha, the `Speaker`s vote` is referred to as the casting vote. The casting vote is a special power that the Speaker of the Lok Sabha has when there is a tie in voting on a particular matter. In such a situation, the Speaker has the authority to cast a vote, which can be used to either break the tie or maintain it. It is important to note that the casting vote can only be used by the Speaker in case of a tie and not in regular voting. This power helps ensure smooth decision-making in parliamentary proceedings.