Listen to the section of the audio clip between 01:02 and 01:33 why does the speaker include a long pause before the sentence beginning then he stirred...?

I’m stuck between C and D, I first thought it was C but many are saying it’s D, I don’t understand how it’s D since the man IS invisible, so I’m not understanding how Ms. Hall was “tricked”

Please answer if you’ve read or heard the (audio)book