Which of the following  best  illustrates a pair of sentences that are joined by an understood relationship?                 a.  luke put three dollars into the office football pool. he was looking forward to vacation.      b.  i don't understand a word you said. have you taken a course in english literature?       c.  detective smiley scanned the dim hallway. he pulled his pistol from its holster.      d.  it rained for ten days and ten nights. grandmother grady called a company to drill a well.