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. it rained for ten days and ten nights. grandmother grady called a company to drill a well.
c. i don't understand a word you said. have you taken a course in english literature?
d. detective smiley scanned the dim hallway. he pulled his pistol from its holster.