Jane and Lucy's father is a teacher
is表示单数,如果是are teachers的话就表示复数
Jane and Lucy's father is a teacher 简和路斯的父亲是教师(两人共有)
Jane's and Lucy'sare teachers 简的父亲和路斯的父亲是教师
Jane and Lucy's father is a teacher
is表示单数,如果是are teachers的话就表示复数
Jane and Lucy's father is a teacher 简和路斯的父亲是教师(两人共有)
Jane's and Lucy'sare teachers 简的父亲和路斯的父亲是教师