同一厂家生产同一商品,有赔有赚。这是因为( )
—What a beautiful key ring! __________is it? —Only 5 yuan.
Jack will have a math test this afternoon. He needs a__________.
You are old enough to make decisions by __________.
There is __________backpack on the desk. It belongs to Tom.
Usually winter ______ December ________ February.