A:a>0
B:a<0
C:a≠0
D:a≠2
The girl__________ swim when she was only four years old. Isn't it amazing?
骏马能历险,犁田不如牛,坚车能载重,渡河不如舟;舍长已就短,智者皆难谋。这一谚语告诉我们( )
藏羚羊是我国特有的珍稀保护动物,要调查藏羚羊的种群密度,最适合的方法是( )