问题
选择题
.She returned home and found that all her furniture by the flood.
A．had been ruined
B．had ruined
C．has been ruined
D．ruined
答案
答案：A
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.She returned home and found that all her furniture by the flood.
A．had been ruined
B．had ruined
C．has been ruined
D．ruined
答案：A
的光源，照射离光源r=5m处的某块金属的薄片. 已知光源发出的是波长
＝663nm的单色光，普朗克常量h=6.63×10-34J.s.