Why Does Cortana Not Appear Until You Have Typed the Whole

Multiple Choice

Why does Cortana not appear until you have typed the whole question?

A) Cortana does not work if you are typing at the same time.
B) Cortana waits until enough information is provided to answer the question before responding.
C) Cortana needs you to hit ENTER before she can respond.
D) Cortana waits for a question mark to be typed before answering.