Which two sentences below are imperative sentences?

A. It is so exciting that you will be joining us for tea!
B. Watch out for the rise in that step in front of you!
C. The forest floor was littered with various colors of leaves.
D. How many buttons do you need to repair your shirt?
E. Make sure that you read your notes carefully to prepare.

B. Watch out for the rise in that step in front of you!

E. Make sure that you read your notes carefully to prepare.

is this correct?

Yes, that is correct. Sentences B and E are imperative sentences.