问题
选择题
There is _____ river at the foot of the mountain(山). _____ river is dangerous.
A．a; A
B．a; The
C．the; The
D．the; A
答案
B
题目分析: 句意：山脚下有一条河，这条河很危险。不定冠词a用于泛指，表数量一个，定冠词为特指。每一次提及某事物用不定冠词，再次提及用定冠词强调，根据there is 可知主语为一条河，故答案选B.