Let's fill in the blanks:
A: The best option here is lives because Polly is a cactus, and the sentence describes a state of being, not an action in progress. Therefore, the answer is 2) lives.
B: The correct option here is waters. Mary is doing an action on Polly, so we need the verb "to water". Therefore, the answer is 2) waters.
C: The best option here is growing because it indicates continuous comparison. Therefore, the answer is 3) growing.
D: The correct option here is little. Polly uses little water, and it needs to be descriptive. Therefore, the answer is 1) little.
E: The correct option is will have. Mary hopes Polly will have beautiful flowers. Therefore, the answer is 2) will have.
So, the complete sentences are:
Polly is a cactus. It lives in a big flower pot. Its owner Mary waters Polly every Thursday before school. Polly is about ten years old. It is growing bigger than other Mary's plants. Mary likes her cactus. Polly uses little water because it doesn't need water very much. Polly is happy. In the future, Mary hopes Polly will have beautiful flowers.