某项任务由子任务Ⅰ（计划编制和批准）和子任务Ⅱ（计划实施）组成。项目经理认为子任务Ⅰ的乐观历时为3天，最可能为4天，悲观历时为8天；子任务Ⅱ的乐观历时为5天，最可能为6天，悲观历时为10天。根据估算，该任务估算历时为（）天。
A.10
B.11
C.12
D.13
参考答案：D
解析：根据三点估算算出每个子任务的活动历时，再根据计划评审技术（PERT）计算出该任务的总工期。三点估算用于估算单个活动的历时，公式为：（最乐观历时+4×最可能历时+最悲观历时）／6。根据此公式，可以计算出子任务Ⅰ的活动历时为4.5天，子任务Ⅱ的活动历时为6.5天。PERT方法中总工期期望值为各活动期望历时之和，所以该任务估算历时为4.5+6.5=11天。
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| I first had physics lessons when I was in Grade Eight some years ago. In class, I 1 that there wasn't a Nobel (诺贝尔) Prize winner from China. That made me sad, and I decided to change (改变) it. 2 after that, I got up early in the morning. I turned on the light and took out a physics book. Then I started 3 quietly. I worked so hard because I had a great 4 - one day, I would be the first 5 person to win the Nobel Prize in physics. Later on, I found physics at school too easy for me. I wanted to lean 6 , so I made a reading plan and started to find answers to more difficult problems. Now I am a top student in physics. I won the first prize in the national physics competition last monh. And I am happy to be closer to my dream after a few 7 hard work. Of course, 8 I have some problems. My classmates always 9 me when they are talking about fashion (时尚) or pop stars, because I know 10 about them. "Well, that doesn't matter too much," I tell myself. "They don't know much about physics , but I won't laugh at them." | ||
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