1851年在英国（）举办世界首次国际工业博览会，展览会的主要场馆时当代采用钢铁和玻璃材料建造的大型建筑（）。
参考答案：伦敦海德公园；“水晶宫”
The “three-point estimates” method for estimating activity duration differs from the “single point, most-likely estimate” method in that it uses ______ .
A．an average of the three estimated durations to estimate activity duration
B．“dummy” activities to represent logic ties
C．“free float” instead of “total float” in the schedule calculations
D．bar charts instead of logic diagrams to portray the schedule
读经纬网和晨昏线图，阴影部分表示夜半球，回答问题。
此日，图中甲地的白昼时间长为（）
A.10时
B.11时
C.13时
D.14时
