【单选题】[单选题]黄昏时视物不清是由于体内缺少( )。
【单选题】—_____ are your father and mother ? —They are fine.
【单选题】Peter: Hi, Jack, _______?
【单选题】设随机变量X与Y的方差均存在且不为0,若E(XY)=EXEY,则( ).
【简答题】How_________your Parents? They are fine. Thank you. (be)
【单选题】—_________ are they? —They are fine. [ ]