【高一英语】有关neither的谓语动词

Both groups are to discuss the generation gap. Neither _____(is/are) sure how well they understand each other.
这里的neither指的是groups.但是,neither=不是这个,也不是那个=两个都不是/两个都没有
因此,groups=单数 了, 因此才会是 is
如： Neither Mary nor Sally likes to drink milk
But neither ______(does/do) they think that it cannot be resolved.
在这里,neither指的是they他们
但他们也不认为这不能解决 因此 do
如：Henry does not want to do the housework. Neither do his two brothers.

is 这个是作主语。
do 后面这个是倒装句，主语是后面的they。
很高兴为你解答！
老师祝你学习进步！
望采纳，多谢你的问题！^_^

你可以把句子还原了再看，前一句是It is sure how well...,。sure是形容词而后一句think是动词