This site says:
Using a plural form of a countable noun when you want to make a general statement about all things of a particular type.
Books are so important in my life. (all books in general)
Apples are delicious. (all apples in general)
So, when we say "Apples" in plural form without "the", we mean "all apples on earth" (in America or in Japan or in supermarkets or etc). It does not matter where they come from as long as they are apples.
So, If that is the case, then "If we use a plural form of a countable noun, then we can not add a prepositional phrase to it right??? Because if we do that, then we break the rule right???"
Let say we add a prepositional phrase "in Japan" to "apples" to form "Apples in Japan are delicious".
But "apples in Japan" refers to a subset of "apples" while "apples" refers to "all apples on earth".
So, "Apples in Japan are delicious" is wrong because "apples" without "the" refers to "all apples on earth".
The above site also says:
You can add a prepositional phrase or a relative clause when you need to show which person or thing you are talking about.
I've no idea about the geography of Scotland.
That is a different man to the man that I knew.
So, change "Apples in Japan are delicious" to "The apples in Japan are delicious"
What does "Using a plural form of a countable noun when you want to make a general statement about all things of a particular type." actually mean?
Does "Apples in Japan are delicious" sound wrong?
Do we have to change "Apples in Japan are delicious" to "The apples in Japan are delicious"
What about "Japanese apples are delicious"?
Note: "Apples in Japan are delicious" = "Apples (that are) in Japan are delicious"