Estábamos sirviendo would be the answer for the nosotros form in the imperfect progressive. For future reference, you should check out the Spanish Dict online, it has all of the verbs in every form and tense :)
For the first part
1. Tu
2. Ella
3. Nosotros
4. Ustedes
5. Yo
4) Dice
it is one person who is SAYING/TELLING that it will rain.
Answer:
This is the answer of your question.
