Final answer:
The appropriate relative pronoun to fill in the blank is 'who'.
Step-by-step explanation:
The appropriate relative pronoun to fill in the blank would be who. The sentence would then read, 'they saw a man in the river who would be an inspiration for them to know how struggle pays in life.'
Relative pronouns are used to connect clauses or phrases to a noun or pronoun and show the relationship between them. In this case, 'who' is used to refer to the man in the river, and it helps identify the man as an inspiration for the students.
Using 'who' in this sentence helps create a clear and concise connection between the man in the river and the idea of struggle paying off in life.
Learn more about Relative pronouns