前肯后否、前否后肯、时态一致、结构一致
一般现在时：They aren’t students,are they
现在进行时：She isn’t waiting for me,is she
现在完成时：Jake hasn't finished his homework,has he
现在完成进行时：Denis hasn't been watching TV,has he
一般过去时：Fanny didn't go home last night,did she
过去进行时：She wasn't sleeping at this time yesterday,was she
一般将来时：We will have wonderful summer holidays,won't we
They won't come back until midnight,will they