Answer: The first sentence.
Step-by-step explanation:
From what I understand, there are two sentences:
First sentence: "this group of wide-eyed boys with a love of the game reminds me of my own freshman squad.though shanna is an underdog in the tournament, skillful coaching is likely to increase her success."
Second sentence: "with a roster full of inexperienced players, the team is unlikely to win a game in the national tournament.milo is an underdog in the tournament because he had only seven wins during the regular seas"
By "optimistic tone", it means a more light, happy tone.
Optimistic definition: hopeful and confident about the future.
The first sentence conveys a positive tone. It focuses on outlooking the downside of the situation, Shanna having a disadvantage, by countering that with correct coaching, Shanna will improve.
The second sentence on the other hand, is focusing on the negatives of their situation. It mentions "inexperienced players", "unlikely to win a game", and "milo is an underdog in the tournament because he had only seven wins during the regular seas". It only looks at the downsides and mentions no solution and no seeming hope to improve.
Hope this helped.