It's not A,B,C because:
NOT-A) If I have to start, I suppose to have already signed SOW. The "was not able to access" suppose I'm trying, so I suppose to have already signed a SOW.
NOT-B) We don't know if we are in a white/black box condition, we can assume for so strict times maybe we are in a white box and we received wrong credentials, but only calling the proper emergency contact for the client can solve this situation(D answer)
NOT-C) Could be a good answer, but to acquire the expected time frame of the assessment doesn't help the assessment team -not able to access and produce results until Monday.
That's why the right answer is D: If I have any doubt or problem or expected time frame compromised, I can advise the emergency contacts.