----Is this the first time you ________ to Harbin?

---- No, but the first time I ____ here, the city wasn’t so beautiful.

A．visited; came

B．visited; have come

C．have visited; have come

D．have come; came

双人上门核实环节的风险主要表现在（）。

A.未执行上门调查

B.担保物真实性存在问题

C.担保人资信不足

D.存在虚假材料