Read the Following and Answer the Question

Read the following and answer the question.
CLIENT (hesitatingly) : I don't know whether I can kick the habit, you know, just let some trivial things go at work and at home. I know I've made a contract with myself. I'm not sure that I can keep it.
HELPER: Um...
CLIENT (pauses, then laughs) : Here I am deep into perfectionism, and I hear myself saying I can't do something. How ironic. Of course, I can. It's not going to be easy, at least at first.
What is the helper's "Um"
Called?

A) An indication that the helper is uncomfortable
B) An attempt to cover up boredom
C) A prompt
D) A probe