The new railway winds its way to Hongkong, _____ mountains _____ tunnels and _____ rivers.

A．across; over; through

B．over; across; through

C．over; through; across

D．through; over; across

证券公司应当建立健全档案管理制度，妥善保管定向资产管理业务的合同、客户资料、交易记录等文件资料和数据，保存期限不得少于( )年。

A．5
B．10
C．15
D．20