甾体皂苷的分子量(),且含有较多的(),不易(),多为无色或白色()粉末,而皂苷元大多有较好的()。
参考答案:大;环;溶水;无定形;结晶
I went to visit him, I found, _____, that he wasn't at home. [ ]
A. however
B. but
C. and
D. so
下列各项中,属于非条件反射的是( )
A.一朝被蛇咬,十年怕井绳
B.画饼充饥
C.谈虎色变
D.跌倒后迅速伸出双手