—Where is your father? —He ______Shanghai on business for several days.
A:has been to
B:has gone to
C:has been in
D:has left for
糖原、核酸、淀粉的基本组成单位分别是
计算﹣12﹣1的结果等于( )
辨形组词。
峭____ 消____
狭____ 峡____