$2)$ Which of the following is true?

A$)$ If she chooses hierarchical clustering, she can choose the number of clusters to use after she performs the clustering.

B$)$ There's no perfect number of clusters to choose, it's really up to her to decide out of the sensible options how many to use.

C$)$ Using $1$ cluster would not be an appropriate choice.

D$)$ A and B

E$)$ All of the above