Please tell me the or the page/exercise you are stuck on, and I will give you the specific answers!

C (The speaker talks about a person who is very ambitious.)

If you are looking for other units, you can generally find the transcripts and keys in the following parts of the textbook ecosystem:

B (The speaker describes a person who is very talkative.) Common Listening Resources

E (The speaker describes a person who is very reliable.)

While I wait for that detail, here are the keys for the first (Unit 1), which is a common starting point for students: Unit 1: Progress Check (Listening)