"AND' or "OR", which is correct?
1). The number of people reaching the age of 100 AND/OR more is increased.
We often use 'AND" following the ages, such as 60 and more, which means the ages more than 60 (include 60), but if we use "OR" in this sentence, does it means the same as the "60 and more"?

2). If you study in A country such as Australia, England OR the USA, your English will be improved dramatically.
I Know the above sentence is right, but if I use "Countries" instead of "A country", can I use "AND" before "the USA", that is:
If you study in countries such as Australia, England AND the USA, your English will be improved dramatically.

If you study abroad such as Australia, England AND the USA, your English will be improved dramatically. Can I say this? Is this sentence correct?

Question

"AND' or "OR", which is correct?
1). The number of people reaching the age of 100 AND/OR more is increased.
We often use 'AND" following the ages, such as 60 and more, which means the ages more than 60 (include 60), but if we use "OR" in this sentence, does it means the same as the "60 and more"?

2). If you study in A country such as Australia, England OR the USA, your English will be improved dramatically.
I Know the above sentence is right, but if I use "Countries" instead of "A country", can I use "AND" before "the USA", that is:
If you study in countries such as Australia, England AND the USA, your English will be improved dramatically.

If you study abroad such as Australia, England AND the USA, your English will be improved dramatically. Can I say this? Is this sentence correct?

Answer

1. OR (Exclusive) 
2a. No, still OR.  (A country - Exclusive)
2b. AND is correct (Countries - Inclusive)

1. In fact we DONT often use 'and' there at all; what you say 'We often use 'AND" following the ages' I feel is not true.  The reason for 'OR' is exclusion, 'AND' is illogical in the sense you cannot be 100 AND more than 100 too.
2a. A country - a single country - but AND would mean more than one.
2b. Countries X, Y,... AND Z - is inclusive because all the countries belong to the 'such countries.  But we are not so pedantic as to mind if you say OR in this case, we are seldom so picky.

Answer

Well, in my view, if you say you study in the countries, such as Australia, England and the USA, then I probably would think you study in multiple countries. For example, you study in Australia first, and later you move to England and begin to study there, at last you go to the USA.

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