根据句意和首字母提示填入所缺单词。

1. －What time (几点) is it?

   －Sorry, I don't have a w_____.

2.  It's an English and Chinese d_____.

3. －My pen is l_____.

    －Don't worry (别担心). Let me help you

4.  How d_____ you spell it?

5.  P_____ call Mary.

大约在70个表型正常的人中有一个白化基因杂合子。一个表型正常、其双亲也正常、但有一个白化弟弟的女子与一无亲缘关系的正常男子婚配。他们的孩子患白化病的概率是多少？ [ ]

A．1/40

B．1/280

C．1/420

D．1/560