Is the underlined verb in the sentence transitive or intransitive? Will you please answer the telephone?

i'm  assuming that the underlined word is answer and i think its transitive. but i'm not completely sure. 

Is this the full answer  Which sentence uses an intransitive verb?                                                                  A. I cheered after finishing the race.   B. My elderly neighbor knitted my sweater.                                                              C. Mr. Phillips called the plumber for help.                                                                  D. Zach used a box for a fort.