Answer:
9. Put your garbage in the can.
10. Is it time to take action?
11. Should we start picking up litter today?
Explanation:
9. You remove "should" because it makes the sentence a suggestion, not a command. Then, you remove "you" because otherwise the sentence would not be grammatically correct.
10. You switch "is" and "it" because when there is a modal verb, you invert the order to form yes or no questions.
Example: She is a firefighter. -> Is she a firefighter?
11. We use "should" to ask what is the ideal or best thing to do. In this case, the question is asking whether it is ideal to start picking up litter today.
