Part a do you think three weeks (21 days) is enough time to observe all of the moon’s phases? why or why not?

No, I don't think so.

Explanation:

The reason is, in order to fully track the moon, you would need about 27 days because that is how long it take the moon to complete one full orbit around the Earth. However, if you don't think that you will need 27 days because some of the days there won't be a phase change then, that is up to you. Hope this helps.

is this a question? wassup