Which one of the following is NOT a trade-off decision that must be made in the development of the project plan

A) Whether to use skilled or unskilled laborers.
B) The amount of profit vendors should make versus the profit other vendors have received in the past.
C) Manufacturing in-house or sub-contracting out the work.
D) The important of cost versus quality.

场景(十) 菜市水利工程项目进行招标，招标人在其行政主管部门领导田某的干预下，选择了甲建筑工程公司并与之签订了施工承包合同。在施工过程中，甲建筑单位未按施工图样中的材料数量进行施工。
根据场景(十)，回答下列问题：

建设工程施工合同属于( )。

A．单务合同

B．双务合同

C．建设工程合同

D．委托合同