用采气管以置换法采集环境空气样品,如果使用二联球打气,应使通过采气管的被测气体量至少为管体积的()倍。
A.1~4
B.2~6
C.4~8
D.6~10
参考答案:D
Miss Li always tries her best to create an atmosphere in class ______ can help her students practice their speaking skills.
A.for which
B.which
C.where
D.of which