为什么entered中,r不双写?

为什么entered中,r不双写? the boy pretended ( )when his mother entered.括号中为什么填 to be reading ERDAS中vector为什么出现editing mode must be entered before any changes what were you doing when the teacher _____the classroomA.entered toB.entered intoC.entersD.entered选什么 为什么 he was still smelling when the door opened and his wife__A.went in B.entered in C.entered D.entered into选哪个?为什么D,B不行? 为什么R要远大于R'图中电阻箱电阻为R',变阻器电阻为R our teacher entered the our teacher entered the room,______book in____ hand.为什么两个空格都不用填冠词, Yes ,but she paid for a ticket when she could have entered free.为什么不用might have entered 急if a trian entered this tunnle ,it would draw in fresh air behind it.为什么用entered? the door opened and（）a middle-aged man in a blue coat a entered b there entered a there entered b in entered选哪个为什么?答案好像是a,是不是答案错了 求公式中为什么要除以r 翻译提问This Nondisclosure Agreement (the Agreement) is entered into by and between Cornerstone R r+ed怎么读:如enter的过去式entered,还有cheered 并联电路中,为什么R1=R2=R,则R并=R/2 在天体运行中,为什么 mg=GMm/r.r=mv.v/r? GMm/r^2=mrw^2 为什么r减少w也减少万有引力公式中R和r表示什么 ..选哪个,为什么请从语法上讲一下选择的原因谢谢啊He was still smiling when the door opened and his wife _________A.went in B.entered in C.entered D.entered into Matlab中为什么X.^2,sin(r)./r中要有个.