Hello

"Riding a car" and "riding on the car" are old fashioned expressions for travelling on a trolley, or "streetcar."

For automobiles, we use "riding in the car," or "riding in a car."

I think this is one case where the "expression" trumps the rules for definite articles.

That is, "the car" often does not refer to a definite car.

(I guess it's arguable. Some people

It is possible...

Past Continuous + Past Perfect.

Like for instance

I was riding on the jeepney when I have read the message.

aerohnI was riding on the jeepney when I have read the message.

The preposition works, but in my opinion the perfect tense does not.

Best regards, - A.

AvangiThe preposition works, but in my opinion the perfect tense does not.

So, it should be:

I was riding on the jeepney when I read the message.

What about this one...

those words or that words?

when I was in highschool, my teacher said that

AvangiThe preposition works, but in my opinion the perfect tense does not.

Right! It's wrong!

aerohnWhat about this one...
those words or that words?
when I was in highschool, my teacher said that those is plural and that is singular.

As a demonstrative pronoun or adjective, "that" is singular. I'm afraid you have misspelled that word.
But you can say, "The words that/which she spoke are still ringing in my ears."

Avangi"The words that/which she spoke are still ringing in my ears."

But how to use the those ? Is there any condition on how to use the plural form of that?

"Those" is always plural - either a demonstrative adjective or a demonstrative pronoun.

"That" is a special case, because it's also a relative pronoun, an adverb, and a conjunction.