尘肺病灶中主要的粉尘为 粉尘,其粒径一般在 以下

A. 粉尘粒径越大，越易引发尘肺病

B. 粉尘中游离二氧化硅含量越高，越易引发尘肺病

C. 接触粉尘时间越长，越易引发尘肺病

A．2

B．3

C．4

D．5

A.3

B.4

C.5

A. 7.1

B. 3

C. 8

D. 5

听力原文：Why did Bill give this advice Why did Bill give this advice Because Tom always d听力原文：Why did Bill give this advice Why did Bill give this advice Because Tom always does ______ of what people have advised.