Hi, Sarah!
For a number of reasons, I'd go with hope. Wording like, "a new torch has been passed" shows hope is pinned on the performance of the new generation, and "united there is little we cannot do" also shows optimism.
Another trick you can use is to look for similarities to eliminate answers. In this case, bitterness and anger are pretty much the same thing. Since there can be only one answer, looking for similarities and eliminating them help you improve your odds if you have to guess.
One last thing - for surprise, you'd need evidence of a "gotcha" or "I've been caught" moment. This passage is mainly about determination and hope for the future.
Good luck in your studies!