水平地面上两个质点甲和乙，同时由同一地点沿同一方向作直线运动，它们的v﹣t图线如图所示．甲做 运动，乙做 运动，在 时乙追上甲，在第4s内，甲的平均速度 （大于、等于或小于）乙的平均速度．
Daniel wishes to d up as a Superman at Halloween next year．
He sent me a few messages， but I （not reply） yet as I don't know what to say．
"When the book （publish） in November， I'm going to donate all the money to help those people in need，" said J．K． Rowling．
Have you found any useful clues， sir？
We （work） on it． There's nothing much I can say at the moment．
Millions of young people （fight） in World War Ⅱ so we could live in peace．
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