The correct answer is (A) The obstruction of legislative action by the use of delaying tactics, such as long speeches, by one or more members of a minority party to prevent the adoption of a particular measure. Also, an unusually long speech, or a series of very long speeches for this purpose.

Examples of use:

• Each member of the minority was determined to speak for up to twenty four hours in order to ensure that the filibuster could continue for several weeks.
  
  
• Once a senator yields the floor to another, he cannot resume his filibuster.