Three of the Olympic Games "all" were stopped

[emsr2d2]

Source: written by a Taiwanese teacher of English.

This suggests you are 100% certain of this.

It's quoted from a practice test, not from a book. Only the publisher knows who wrote the practice tests.

This suggests that you actually have no idea who wrote them.

I don't know who wrote the questions, but I am sure that they were written by Taiwanese teachers.

This doesn't make sense.

I'm going to ask you to stop posting these excerpts until a) you can cite the source in full and b) you explain how our assistance is helping you. (If you're forced to teach using the material, your students are forced to use it, and you're not in a position to tell your students or your superiors that the material is tripe, I really can't see how commenting on/correcting it is a good use of our time, or yours.)

 

[teechar]

Repetition. I and others have already said that it should follow “were” and that “all” is optional

I don't agree with you, so it's not repetition. I think "all" is wrong in that sentence.

 

[PaulMatthews]

I don't agree with you, so it's not repetition. I think "all" is wrong in that sentence.

On what grounds?

The adjunct "all" is commonly used to emphasise totality.