下图是一个氢核磁共振谱,请你观察图谱,分析其可能是下列物质中( )
A.CH3CH2CH2CH3
B.(CH3)2CHCH3
C.CH3CH2CH2OH
D.CH3CH2COOH
答案:C
Harry is my neighbour. He is also a good friend of mine. [ ]
A. less than
B. at least
C. at most
D. more than
在青铜中,为加强硬度,应该添加哪种元素的剂量()
A.铅
B.铜
C.锡
D.铝