某物质可能含有炭粉、碳酸钙、氧化铜、氧化铁中的一种或几种,现进行如下实验:(1)取样品,加热至高温,产生一种能使澄清石灰水变浑浊的无色气体。(2)往冷却后的固体残渣中加入足量的稀盐酸,固体残渣全部溶解,同时产生一种可燃性气体。根据以上实验推断:该固体一定含有_____________,一定不含有______________,可能含有_____________(以上各空填写化学式)
We must be careful to avoid (make) mistakes in the exam.
It's very (polite) to talk loudly in public.
Subways make our lives (easy) than before.
Now many wild animals are in (dangerous). We should protect them.
To my disappointment, the new movie is so (meaning).