OG12thGMAT句子分析上题
in1995Richard.Stallman,awell-knowcriticofthepatentsystem,testifiedinPatentOfficehearingsthat,totestthesystem,acolleagueofhishadmanagetowinapatentforoneofKirchoff'slaw,anobservationaboutelecticcurrentfirstmadein1845andnowinvirtuallyeverytextbookofelementaryphysics.
testifiedinPatentOfficehearingsthat中that是什么作用?hearing怎么理解?testifyin.这个是主句吗?