某物体在一足够大的光滑水平面上向西运动，当它受到一个向南的恒定外力作用时，物体将做（　　）

已知向量 $\overrightarrow{a}=\left(1,\sin \theta \right)$ ， $\overrightarrow{b}=\left(1,\cos \theta \right)$ ，则 $\left|\overrightarrow{a}-\overrightarrow{b}\right|$ 的最大值为____．

任务型阅读，每空一词。   

    There are some differences between British English and American English. In grammar, for example, speakers of British English say "in hospital" and "Have you a pen?". Americans say "in the hospital" and "Do you have a pen?". Pronunciation is sometimes different. For example, when a learner speaks British pronunciationda:ns (dance), he may not understand the American pronunciationdæns. There are differences between British English and American English in spelling. For example, "travelled" and "honour" are British spelling, "traveled" and "honor" are American spelling. However, in most situations(情况), British English and American English are not different languages.

____ between British English and American English
	British English	American English
In grammar	In ____	In the hospital
In ____.	travelled	traveled
____ is sometimes different	da:ns	dæns
Usually, British English and American English are the ____language.

2012年12月12日，朝鲜发射光明星3号卫星对此，日、韩、美等国表示强烈谴责，并要求采取进一步制裁措施。中方则认为，朝鲜有和平利用外空的权利，但必须遵守联合国安理会做出的相关规定，呼吁各方保持克制冷静应对。对此，认识正确的是
①独立自主是我国外交政策的基本立场
②和平与发展已经不是当今时代的主题
③维护国家利益是主权国家对外活动的出发点和落脚点
④维护世界和平促进共同发展是我国外交政策首要目标

某电热水器，额定功率为2000W．当热水器正常工作40min时，可将50kg的水从20℃加热到40℃．水的比热容为4.2×10³J/（kg•℃）．试求：