如图所示，电源电压保持不变，当开关S接触a时，电流表的示数为0.3A，R₁消耗的功率为0.9W；当开关S接触b时，电流表的示数为0.2A，R₂消耗的功率是0.8W，则R₁=______Ω，电源电压U=______V．

Little ____that we were watching his every move, so he seemed to be going his own way in this business.

A．he realized

B．he didn’t realize

C．didn’t realize

D．did he realize