某运输企业一季度末有营运车辆100辆，其中一级车50辆，二级车30辆，三级车10辆，

小麦、玉米、水稻等植物的茎不能逐年加粗，原因是其茎的结构中不具有

A．形成层

B．木质部

C．韧皮部

D．髓部

Many black children died ___ cold and hunger in Africa.

A．of

B．in

C．on

D．for

We’ll climb the mountain _______ the weather is bad this weekend.

A．if

B．when

C．until

D．unless

在Excel中，想要删除已有图表的一个数据系列，不能实现的操作方法是（）。

A.在图表中单击选定这个数据系列，按“Delete”键

B.在工作表中选定这个数据系列，执行“编辑→清除”菜单命令

C.在图表中单击选定这个数据系列，执行“编辑→清除→系列”命令

D.在工作表中选定这个数据系列，执行“编辑→清除→内容”命令

Critical chain is a schedule network analysis technique that modifies the project schedule to account for limited resources. Critical chain combines deterministic and probabilistic approaches. Initially, the project schedule network diagram is build using non-conservative estimates for activity durations within the schedule model, with required dependencies and defined constraints as inputs. The critical path is then calculated. After the critical path is identified, resource availability is entered and the resource-limited schedule result is determined. The resulting schedule often has an altered critical path. The critical chain method adds non-work schedule activities to maintain focus on the planned activity durations, also referred to as ______ .

A．duration buffers

B．resource leveling

C．reverse resource leveling

D．crashing