传粉受精后,花的子房发育成____; 胚珠发育成____;受精卵发育成____.
—I didn't hear you come in just now.
—That's good. We tried __________ any noise, for you were sleeping.
世界三大宗教创立的先后顺序是( )
如图所示,一倾角为45°的斜面固定于竖直墙上,为使一光滑的铁球静止,需加一水平力F,且F过球心,下列说法正确的是( )