这是一个优秀的班集体，在这个班级，同学们具有强烈的竞争意识，你追我赶；同时，班内同学有新的学习资料，也总是放在“推荐窗”里，供大家使用。这给我们的启示是（   ）
①竞争和合作是相互依存的  ②合作比竞争更重要  ③竞争中需要合作，竞争最理想的结果是“双赢” ④生活中既有竞争，也有合作 

在平面直角坐标系xOy中，过原点O及点A（0，2）、C（6，0）作矩形OABC，∠AOC的平分线交AB于点D．点P从点O出发，以每秒$\sqrt{2}$个单位长度的速度沿射线OD方向移动；同时点Q从点O出发，以每秒2个单位长度的速度沿x轴正方向移动．设移动时间为t秒，当t为____时，△PQB为直角三角形．

阅读下面短文，按要求完成各项任务．

    Everywhere in the world there are different ways of behaving．When we meet someone，everything we say and do expresses our cultural background．So if you want to get on with someone from another culture，it helps to understand something about these differences．

    Even how we stand depends on our culture．English people talk to each other at an average （平均的） distance of 130 cm，while Italians chat at an average distance of 80 cm．So Italians can think that English people are unfriendly because they stand too far away!And English people can think that Italians are too close．

    Touching is also cultural．The French touch much more than Americans．A French couple may touch 100times in half an hour while an American couple may only touch twice!And French teenagers touch each other much more than American teens．