A.1:1 B.1:10 C.1:25 D.1:50
A.0° B.10~20° C.90° D.30~45°
A.水體無(wú)污染 B.水體正在自?xún)?br /> C.水體已經(jīng)自?xún)?br /> D.不能說(shuō)明問(wèn)題