个人(包括个体户和自然人)只要发生应税行为都应办理税务登记。( )
参考答案：错
解析： 《税务登记管理办法》第2条。
31. ________was difficult to save the places and buildings _____destroying their old beauty.
A．That…unless
B．This…except
C．It…without
D．There … except for
变管径流动中，D1=400mm，D1=200mm。流速v1=2m/s，则流速v2为（）。
A.2m/s
B.4m/s
C.8m/s
D.16m/s
the places and buildings _____destroying their old beauty.