【简答题】潜水艇是靠改变______来实现浮沉的.飞艇的气囊里装着______比空气小的气体,当它受到的浮力______重力时就能上升(选填“大于”、“小于”或“等于”).
【单选题】This boy was _______ for what he had done in the class.
【多选题】以下哪几项可以用于脑儿翻身运动的训练( )
【单选题】(2013·高考天津卷)At our factory there are a few machines similar to ________ described in this magazine.
【单选题】“九拜”出自《周礼》,是我国古代特有的向对方表示崇高敬意的跪拜礼。下列不属于九拜的是( )。