Tom's and Mary's room后面的room要不要加S,Why?

She is Mary and Tom’s sister.这句话对吗?A．Mary’s and Tom B．Mary’s and Tom’sC．Mary and Tom’s this is( )room.A.Tom and Mary's B.Tom's and Mary's C.Tom's and Mary D.Tom and Mary _____school bags are on the desk .A.Mary and Tom's B.Mary's and Tom's C.Mary's and Tom (Mary and Tom)math teacher 's 应该加在哪?如题是Mary‘s and Tom's math teacher还是Mary and tom' math teacher Tom's and Mary's room后面的room要不要加S,Why? Mary’s going swimming and（ ）so is Tomso has Tomso Tom isso Tom has Tom and Mary’s father 这是Mary的父亲,还是Tom和MarTom and Mary’s father 这是Mary的父亲,还是Tom和Mary这两个人的父亲. Tom and Mary's mother 可以表示为（Tom与Mary是兄妹）吗?Tom and Mary's mother 可以表示为（Tom与Mary是兄妹）吗? Tom,Mike,and Mary were classmates of Stephen's 's怎么理解呢 （ ）schoolbags are these?They are Tom's and Mary's. -----____school bags are these?-----They are Tom's and Mary's.A.Whom B.WhoseC.Who mary and jim’s和mary’s and jim’s 这句英语里用is还是are?Tom's ,Mary's and Bob's birthday is in May.还是应该是Tom's ,Mary's and Bob's birthday are in May. Mary is Tom's girl f-----. Mary and Tom's room 是2个人一个房间吗? Bob and Mary are Tom’s p( ),he is their son.括号里填什么 Tom's mother is _____(thin) than Mary's This is tom'S friend in america.改为复数形式 This is mary's father and mother.同义句