一家公司在生产中有以下的零件需求。每天需要的零件（单位）可能性500.2600.5700.2800.11.0为了确保存货数量在90%的情况下是充足的，每日的期初零件余额应该是（）。
A．50
B．60
C．70
D．80
参考答案：C
解析：
70个单位的供应量确保了90%的概率可以满足日常需要(0.2+0.5+0.2=0.9)。选项(a)不正确，50个单位的供应量只能确保20%的概率满足需要(0.2)。选项(b)不正确，60个单位的供应量只能确保70%的概率满足需要(0.2+0.5=0.7)。选项(d)不正确，80个单位的供应量能够确保100%的概率满足需要(0.1+0.5+0.2+0.1=1)。
| 完形填空 | ||||
| One Hour of Time A man came home from work late again, tired and annoyed, to find his 5-year-old son waiting for him at the door. "Daddy, may I ask you a 1 ?" "Yeah, sure, what is it?" replied the man. "Daddy, how much money do you _ 2 an hour? " "That's none of your business. What makes you ask such a thing?" the man said 3 . "I just want to know. Please tell me: how much do you make an hour?" insisted the little boy. "If you 4 know, I make $20 an hour. " "Oh," the little boy replied, head bowed. Looking up, he said, " Daddy, may I 5 $10 please? " The father was angry. "If the 6 reason you wanted to know how much money I make is just that you can borrow some to buy a 7 toy or some other nonsense, then you march yourself 8 to your room and go to bed. " The little boy quietly went into his room and 9 the door. The man sat down and started to get even madder about the little boy's 10 . After an hour or so, the man had 11 . The man went to the door of the little boy's room and opened the door. "Are you 12 son?" he asked. "No, Daddy, I'm awake," replied the boy. "I've been thinking, maybe I was too 13 on you earlier," said the man. "Here's that $10 you 14 ." The little boy sat straight up, 15 . "Oh, thank you Daddy! " he yelled. Then, reaching under his pillow, he pulled out some 16 bills. The little boy slowly 17 out his money, and then looked up at the man. "Why did you want more money if you 18 had some?" the father asked angrily. "Because I didn't have 19 , but now I do,"the little boy replied. "Daddy, I have $ 20 now. Can I buy an hour of your 20 ?" | ||||
|