Yesterday Frank worked deep into the night, this is the   second time this week he's stayed up, ____  ?    [ ]

A. didn't he          

B. isn't it        

C. isn't this  

D. hasn't he

s12和s2已正确定义并分别指向两个字符串。若要求：当s1所指串大于s2所指串时，执行语句S;则以下选项中正确的是

A．if(s1>s2)S;

B．if(strcmp(s1,s2))S;

C．if(strcmp(s2,s1)>0）S;

D．if(strcmp(s1,s2)>0)S;