Answer:
B. When an unsuspecting fish or crab wanders by
Step-by-step explanation:
If he writes any of the other things, he might think it's funny, but it could come off as fooling around. To some teachers, it could look like he isn't taking the assignment seriously. While teachers grade assignments, they check for proper grammar, punctuation, and formal writing, which could all be bonus points on your assignment/report/essay.
Hope this helps! :)