Read the excerpt from The Diary of Anne Frank.

Mr. Frank. Now. About the noise. While the men are in the building below, we must have complete quiet. Every sound can be heard down there, not only in the workrooms, but in the offices, too. The men come at about eight-thirty, and leave at about five-thirty. So, to be perfectly safe, from eight in the morning until six in the evening we must move only when it is necessary, and then in stockinged feet. We must not speak above a whisper. We must not run any water. We cannot use the sink, or even, forgive me, the w. c. The pipes go down through the workrooms. It would be heard.

Why must the Frank and Van Daan families most likely stay quiet during the day?

They do not know whether they can trust the others who work in the building.
They are embarrassed to be living in an office building.
They are worried that others in the building may want to join them.
They do not want anyone who works in the building to get captured.