胺类用醇烷基化既是连串反应,又是可逆反应。
参考答案:对
He had little idea that it was getting so late, ________?[ ]
A. didn't he
B. wastn't it
C. did he
D. was it
东方式倾斜型插花第一主枝的角度大约为()度的范围。
A.0-15
B.30-60
C.75-90
D.45-90