现有(NH4)2SO4、NH4Cl、K2SO4三种无色溶液,要将它们一次鉴别出来,则选用的试剂是 [ ]
A.氯化钡
B.硝酸银
C.氢氧化钠
D.氢氧化钡
答案:D
The children talked so loudly at dinner table that I had to struggle . [ ]
A. to be heard
B. to have heard
C. hearing
D. being heard
中国古代的三垣四象二十八宿分别是?