Working crossword puzzles, the airlines passenger passed the time while waiting for his flight.

identify the phrase in bold.

a.
appositive phrase

b.
prepositional phrase

c.
participial phrase

d.
gerund phrase

mark twain, real name samuel langhorne clemens, was an american writer, humorist, entrepreneur, publisher, and lecturer. among his novels are the adventures of tom sawyer and its sequel, the adventures of huckleberry finn, the latter often called "the great american novel". wikipedia