Our hometown is more beautiful than before,（isn't) it?
这是反义疑问句.
Swimming in the pool with friends （C） very interesting.
A;has B;have C;is
“Swimming in the pool with friends ”指一件事,为单数.is+interesting形成系表结构.
Some of my classmates （C） from other cities.
A;comes B;is C;are
“Some of my classmates”我的一些同学,为复数,使用are
This is my twin sister Lucy.Both she and I （ C ）good at drawing.
A;am B;is C;are
Both……and……谓语用复数形式.
The professor,together with his son,（ B ）Lanzhou_Beijing.
A;have left;for B;has left;for C;have left;to
The professor主语为单数,together with his son只是一个插入语
My family（ A） having supper when suddenly the bell rang.
A;is B;was C;were
My family我的家人（我们一家）,作为一个整体.
The singer and dancer （A） come to our school.
A;have B;has C;were
and并列singer 和 dancer ,为复数,谓语用have
A number of children （B ）for the teacher to come now
A;is waiting B;are waiting C;waits
A number of大量的……,谓语用复数形式
The students each （A ）a dictionary now.
A;has B;have C;has got
each 每个人,所以是单数.
如有不懂,再行探讨,