I _____ he park last week. [ ]
A. have been to
B. has been to
C. went to
D. was going to
答案:C
右图中,甲是相对分子质量为16的有机物,乙是最常见的溶剂,丁是白色难溶固体,其中金属元素的质量分数为40%.甲的化学式 .②和③的化学方程式分别为 和 .丙的一种用途是 .
患者女,15岁,荨麻疹病史1月,其皮损主要为()
A.红斑
B.丘疹
C.风团
D.结节
E.渗液