Select the answer choice in which a dependent clause is underlined.
a. Edgar Allan Poe is considered to be the inventor of the detective story.
b. Writers all over the world have imitated his tales of mystery and supernatural events.
c. He earned his living as a writer, but he was in financial difficulties for
most of his short life.
d. Though the cause of Poe's death is unknown, many believe that poor
health and habits were probably the main factors.