Which of the Following Definitions Most Obviously Fails to State

Multiple Choice

Which of the following definitions most obviously fails to state any essential attributes?

A) The Olympics is an international competitive sporting event.
B) An airplane is a flying machine that is used for transportation.
C) A regular octagon is a closed plane figure with eight equal sides and eight equal angles.
D) An angel is a divine messenger.
E) Cork is one of the major exports of Portugal.