4[单选题]
<p style="FONT-SIZE: 12pt; MARGIN: 0cm 0cm 0pt; FONT-FAMILY: 'Times New Roman'"><span>It's twelve o'clock, I think I must be off now.</span></p>
<p style="FONT-SIZE: 12pt; MARGIN: 0cm 0cm 0pt; FONT-FAMILY: 'Times New Roman'"><span>Oh,really? I<u><span>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; </span></u><span>&nbsp;</span>it at all.</span></p>

A.don't realize

B.haven't realized

C.didn't realize

D.hadn't realized