Dennis's room 对还是Dennis' room对?

Dennis's room 对还是Dennis' room对? Dennis's 还是Dennis' 人名以s结尾的是加'还是’s?人名：Dennis Dennis likes to hear granny's bedtime s_____. He's cleaning his room.对cleaning his room提问. 是Tom’s and Sam’s room 还是Tom and Sam’s room? where's Mr White? He’s in room 202还是Room 202? I don't like Dennis's show,because it's the most t_______. any rooms available还是any room available 为什么有加s. He's cleaning his rooms对claning his room提问 是The student's reading room还是the students' reading room阿? 改为同义句：She played the piano better than Dennis.Dennis played the piano worse than she.这样对i不对 living room,attic,bathroom,bedroom,kitchen,basement,staircase,office/study/den,dining room的中文意思 以S结尾的名词变成所有格时怎么变?如dennis a big nice room 还是 a nice big room 对呢?为什么? across room还是through room Peter’s room is larger than Sam’s.对Peter’s 提问 I am going to my mother's room.(对划线部分提问）划线部分：my mother's room