问题描述：
用适当的介词填空 in on under
in on under behind to of next to
Li lei is ________duty today.
Lily sits ______ lucy.
who's________the photo?
There is a door____the wall.
in on under behind to of next to
Li lei is ________duty today.
Lily sits ______ lucy.
who's________the photo?
There is a door____the wall.
问题解答：
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