The precious manuscripts were hopelessly （） by long exposure in the cold, damp cellar.

单项选择题The old couple decided to （）a boy and a girl though they had three children of their own.

A．adapt
B．bring
C．receive
D．adopt

单项选择题Desert plants（） two categories according to the way they deal with the problem of surviving drought.

A．break down
B．fall into
C．differ in
D．refer to