Final answer:
The sentence that is an opinion is 'This became a fantastic way to make friends, but it was more than that', as it contains subjective evaluations.
Step-by-step explanation:
The sentence expressing an opinion from the given passage is: "This became a fantastic way to make friends, but it was more than that." (paragraph 6). This sentence contains words that evaluate the worth of the event described ('fantastic', 'more than that'), which are subjective and represent the speaker's viewpoint, rather than stating a fact that can be proven true or false.