科学家估计,现今地球上约有___________多万种生物。
250
Not until all the fish died in the river ____ how serious the pollution was. [ ]
A. did the villagers realize
B. the villagers iealized
C. the villagers realized
D. didn't the villagers realize
Responsibilities()becoming a father.
A.charge for
B.go with
C.save for
D.go through