Answer:
1. A. either we can go upstream, or we can try to catch fish here.
2. A. Chris not only forgot his notebook, but he also forgot his homework.
3. A. On her way to the park, Letty found both a purse and a cell phone.
4. D. both/and
5. D. not only were we going to ride the Ferris wheel, but we were also going to watch the fireworks!