Gerund as it functions as a subject of your sentence as well.
C. Necessary is the answer
Answer:
Well, if your list contains:
A. A group of friends hang out and go to the movies.
B. Hikers get caught in a snow storm and must find shelter.
C. Stranded on a boat, a man must fish to survive.
D. The main character builds sandcastles.
Then, the answer would be B).
Explanation:
Hikers get caught in a snowstorm and must find shelter.
