听叙述,根据听到的内容推测并回答相应的问题。每道叙述将播放两遍。(共5分,每小题1分)例:(C)What is she going to do?(1)Which backpack is she going to buy?(2)what should she do before she goes to bed?(3)What is Bob going to make?(4)What is he going to do?(5)What should Amy do?
已知,集合,.若,则的值是
已知,则向量与向量的夹角是()
在平行四边形中,与交于点是线段的中点,的延长线与交于点.若,,则()
下列命题中,正确的是()
设正方体的棱长为,则它的外接球的表面积为 ()