The problem ________ when the students refused to do their homework.
A
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________ to the papers is restricted to Defense Department personnel only.
________withthesizeofthewholeearth,thehighestmountainsdonotseemhighatall.
Human behavior is mostly a product of learning ________ the behavior of animals dependsmainly on instinct.
Theassociationis________toraisingfundstohelptheblind.