Which sentence has a formal tone? A. The author tells all about the life of a hyena in Africa.
B. As human populations expand, the hyena is losing much of its
natural habitat.
C. The book I just finished was really good.
D. It makes me really sad that they can't run and play freely anymore
without being threatened.

Aman lives on the twelfth floor of an apartment building. every morning he takes the elevator down to the lobby and leaves the building. in the evening, he gets into the elevator, and, if there is someone else in the elevator -- or if it was raining that day -- he goes back to his floor directly. otherwise, he goes to the tenth floor and walks up two flights of stairs to his apartment.