The answer you are looking for is option A. they feel it is an unnecessary risk to their safety.
Alfred Dussel is a fussy old dentist who also lived in the Secret Annex with the Franks and the van Daans. He frequently endangers the other members of the Secret Annex by breaking their security rules and even hoards food, which he refuses to share. Overall, he fights with everyone in the Secret Annex and often gives people the silent treatment.
During the daytime hours, the residents of the Secret Annex read books and slept. They could not make any noise like talking, flushing the toilet, moving furniture, and walking around. In the evenings, mostly after 5 o’clock, they could move around and listen to the radio. They read books, played games, danced, and studied languages, mythology, religion, ancestry, math, history, to pass time during the night.