Question

The _____ is a rule unique to the u.s. senate that allows any senator to hold the floor indefinitely and thereby delay a vote on a bill to which he or she objects.

Answer 1

The correct answer is filibuster.
This is not really unique to the US Senate as the filibuster comes from Ancient Rome, and today it is used all over the world, in countries such as United Kingdom, Australia, New Zealand, etc. However, it is the most powerful tool in the US Senate, where it is also referred to as 'talking a bill to death,' where senators can delay or prevent a bill from ever becoming a law if they disagree with it.