单项选择题
A.1/3倍 B.2/3倍 C.1倍 D.不能确定
A.MR=2 B.MR=4 C.MR=18 D.MR=1
A.MR=MC B.MR=LMC=SMC=LAC=SAC C.MR=LMC=SMC,AR=LAC=SAC D.MR=LMC=AMC