bill's and sam's project ____about yogurt

bill's and sam's project ____about yogurt bill's and sam's projects ____about yogurt.用are both 还是both Tom's hair is shorter than------ A.Sam and Bill B.Sam and Bi he's sam and amy's friend. 是Tom’s and Sam’s room 还是Tom and Sam’s room? THE desk belongs to A：Bill and Mike‘s B：Bill’s and Mike 's C they did a s ____about learning English. Lucy and Lily are s( ) and they look the sam 单选、 ____mother is a teacher.A.Tom and Bill B.Tom's and Bill' John is Sam and Amy's friend.是否有语法错误? what's really interesting about Sam and his sister sam's parents____dancing and singing in the party