Having been told that her son died in the accident, the old woman appeared very calm, as if nothing （）.

A.that
B.which
C.what
D.whose

A．Different aspects (方面) of an urban environment, such as the crowded streets, can lead to an increase in self-control.
B．Small changes in urban design, cannot reduce the negative side effects of city life.
C．For the first time in history, the earth’s population is more urban than rural.
D．A walk down a busy city street will improve brain performance.