26．The chemical weapons      by the Japanese troops are the chief cause of the constant poisoning accidents.

A．Were abandoned

B．abandoned

C．had abandoned

D．abandoning

下列合同和施工承包合同有主从关系的是（）。

A．勘察设计合同

B．履约担保合同

C．监理服务合同

D．设备安装合同