用化学用语填空:
(1)氦气____ . (2)五个碳酸根离子____ .
(3)两个氯原子____ . (4)最简单的有机物____ .
写出近义词
喧闹—____ 平静—____ 兴奋—____
如图甲所示,一辆搬运砖头的独轮车,车箱和砖头所受总重力G=1200N,推车时人手向上的力F应为____ N.如图乙所示的动滑轮,支点为O,则动力臂LF是阻力臂LG的____ 倍.
He is a strict teacher, but all the students like him. I don't know why.
—Two windows.