His jokes made all of us _____. [ ]
A. laugh
B. laughing
C. to laugh
D. laughed
答案:A
硼的最高价含氧酸的化学式不可能是()。
A.HBO2
B.H2BO3
C.H3BO3
D.H2B4O7
我国《室内空气质量标准(GB/T18883-2002)》规定要求,室内SO浓度1小时均值在()
A.≤10mg/m3
B.≤0.50mg/m3
C.≤0.24mg/m3
D.≤0.60mg/m3
E.≤1.0ng/m3