C. She wonders if it is safe to meet Aslan.
She says in the text, "Is he-quite safe? I shall feel rather nervous about meeting a lion". The other options address some of Susan's character traits in that she does want to make a good impression and she is hoping that Aslan will be able to help them. However, her initial concerns are about the fact that Aslan is a lion, and normally people are afraid of lions.
