It was evening ______ they reached Haikou City.
A.that
B.until
C.since
D.before
答案:D
已知某气体是与O2形成的混合物,经分析得知,该混合气体中,硫元素的质量分数为15%,则该混合气体中氧气的质量分数为( )
A.45%
B.55%
C.60%
D.70%
群众性是( )的特点。
A.和解
B.调解
C.仲裁
D.诉讼