his parents are teachers中的谓语是什么?是are还是are teachersare不是连系动词吗,它不是应该和表语（teachers）构成谓语吗?主要是下面的问题

his parents are hard on they are his parents改成一般疑问句 These ____ (watch) are from his parents. they are his parents改成一般疑问句 His parents are quite _(worry).为什么? Are these his parents?改为肯定句 Those are his parents改同义句 Those are his parents.（单数） His parents are quite __(worry). Are these his parents?(改为肯定句) His parents are English 改为同义句 His parents are both teachers.和His parents both are teachers.哪句才对? His parents are always w_____ about his health. His parents are always () about his health.越快越好, His parents are doctors.中的are doctors是什么语 His parents are very healthy.（改为同义句） His parents are_____ ______ ____ Tom and his parents live on a farm.his parents are farmers. _______ pleased with his homework.A．His both parents are B．His parents are both C．All his parents are D．His parents are all请讲明白