Which word shows the best meaning of the underlined word in this paragraph?

My grandparents are taking a trip for their fiftieth anniversary celebration. Part of it is a train excursion that is to last eight hours. That includes three hours for lunch and shopping. They are also taking a side expedition to a cave.

A.
journey

B.
passage

C.
tunnel

D.
exercise

(the underline word is excursion)