Answer:
They do not know whether they can trust the others who work in the building.
Step-by-step explanation:
The Diary of Anne Frank is a first-person’s account of a young girl named Anne Frank. The book contains her narrative of their life in the secret Annex, hiding from being captured by the Nazi Germans.
In the given excerpt from Mr. Frank's dialogue, we get to know that the need for silence during office hours is a must for the people in hiding. It was to ensure that they are not heard of by the office workers and thus, guarantee their safety. Mr. Frank told them not to make a sound beyond a whisper, and not to do anything that produces a sound or the workers may hear them. This need to be quiet during the day is because they do not know if they can trust the workers with their safety.
Thus, the correct answer is the first option.