Tom was a student at this university from 1999 to 2003, ____ he studied very hard and was made

Chairman of the Students' Union.  [      ]

A. for which time  

B. during which time    

C. during whose time    

D. by that time

阅读以下说明和C函数，将应填入__(n)__处的语句或语句成分写在答题纸的对应栏内。　　

【说明1】函数deldigit(char *s)的功能是将字符串s中的数字字符去掉，使剩余字符按原次序构成一个新串，并保存在原串空间中。其思路是：先申请一个与s等长的临时字符串空间并令t 指向它，将非数字字符按次序暂存入该空间，最后再复制给s。【C函数】　　

【说明2】函数reverse(char*s，int len)的功能是用递归方式逆置长度为len的字符串s。例如，若串s的内容为"abcd"，则逆置后其内容变为"dcba"。【C函数】　

空（5）应填为。