What is a past participle and when should i use it?

Question

Take for instance the following:

In the past, people _______ by horse carriages.

Should it be have traveled; had traveled; traveled; were traveling. And why?

I'm studying for an exam and for the life of me I can't remember this.

Answer 1

traveled is a past participle.

"had traveled" and "were traveling" don't sound right.

Answer 2

used to travel

because they don't anymore but if it should be one of the choices you said then I'll say traveled because something happened in the past and the action is finished right now

generally,you use have traveled when you can feel the effect of it right now while the action has happened in pas itself.

you use had traveled when something happenED in past before another(both of them happened in the past)

were traveling is usually used when an action in past was interrupted by another one:I was walking when suddenly I saw john

seeing john has interrupted walking

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