单选题 For an activity，the optimistic，most likely and pessimistic estimates are 12，16 and 18 respectively．Which of the following statement is correct?

A、 There is 68.26% chance that the activity will be completed in 15 to 17 day
B、 There is 95.44% chance that the activity will be completed in 15 to 17 day
C、 There is 68.26% chance that the activity will be completed in 14.67 to 16.67 day
D、 There is 93.73% chance that the activity will be completed in 15 to 17 day

【正确答案】 C

【答案解析】[解析] 某个活动，最乐观的估算是12；最可能估算是16；最悲观估算是18。下列哪个说法是正确的? A) 有68.26%的概率，活动将在15～17天之内完成。 B) 有95.44%的概率，活动将在15～17天之内完成。 C) 有68.26%的概率，活动将在14.67～16.67天之内完成。 D) 有93.73%的概率，活动将在15～17天之内完成。该活动平均估算值是15.67；标准差是(18-12)/6=1；14.67到16.67之间正好左右各一个标准差。概率为68.26%。