倒装句中有时用do,did,does,有时用have,has,had,什么时候用助动词,什么时候用系动词?People seldom did experiments to test their ideas in those days.改倒装句Seldom did people do experiments to test their ideas in those days这里的考点,有没有类似的题目

英语动词分为及物动词,不及物动词,连系动词,反身动词,实义动词,助动词,限定动词,非限定动词和短语动词.
1.及物动词和不及物动词：动词根据它在句中是否跟宾
语,可分为及物和不及物,但是有的动词既可以做
及物也可做不及物,比如fly
Boys fly kites(及物）
Birds fly(及物）
2.连系动词：连系动词表示不完全谓语关系的动词,
它仅说明真正的谓语（既表语）在其后.
比如：
I am very hungry and tired(表语是形容词）
He was a painter,a very bad one(表语是名词）
常见的连系动词有become,appear,get look,
remain,seem 等等.
3.助动词分为时态助动词和情态助动词.
助动词本身无实际意义或者意义不完全,不能单独
做谓语.时态助动词有：do,be,have ,shall
(should),will(would)等等.它们在句中和实义动
词一起构成各种时态,语态,语气以及否定和
疑问结构.比如：
Does he have coffee with his breakfast?
Do not be so careless.
The thief was caught in the parking lot.
4.情态动词有shall,should,will,could would,
may,might,must,dare ,need,ought to 等等,
其用法与助动词相同.比如：
you should have reported the matter to the
police.
I may have met him before.
You needn't come so early.
They dare not tell the truth.