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【单选题】
波长l=550 nm(1nm=10−9m)的单色光垂直入射于光栅常数【图片】的平面衍射光栅上，可能观察到的光谱线的最大级次为A.
2
B.
3
C.
4
D.
5
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皮皮学刷刷变学霸
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【简答题】Who lived in the building at the time of the fire? Only a few ______.
【单选题】The alarm signal for engine room catching fire is a blast of random bell followed by____.
A.
two knocks
B.
three Blocks
C.
four knocks
D.
five knocks
【单选题】The alarm signal for engine room catching fire is a blast of random bell follow by ____.
A.
two knock
B.
three knocks
C.
four knocks
D.
five knocks
【单选题】大火把树林烧得仅剩下几课树。
A.
The fire reduced the forest to a few trees.
B.
The big fire burnt the forest to a few trees.
C.
The big fire burnt severl trees in the forest.
D.
The fire made many trees burnt in the forest.
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