Upon into the blue sky when we passed by its nest.
A. did the bird fly
B. flew the bird
C. the bird flew
D. had the bird flown
网友回答
A. did the bird fly
(答案→)B. flew the bird
C. the bird flew
D. had the bird flown
解析：句意：当我们经过鸟巢的时候，这个鸟飞上蓝色的天空。表示方位的副词Upon及介词短语置于句首，名词作句子的主语时，句子的主谓用全部倒装。谓语动词提到主语前面，所以选B。