I often have conversations with John over ______ telephone, while I keep in touch with Tom by ______ letter.

A．/;the

B．/;a

C．the; /

D．the; a

读东南亚某海岛等高线图，

图中甲、乙两河（）

A.均以雨水补给为主

B.均有较短的冰期

C.甲河流域面积大于乙河

D.乙河落差大于甲河