Would anyone please tell me which one of the following is correct? (underlined part)

1. 'the' can be used before both singular and plural nouns.

2. 'the' can be used before both singular nouns and plural nouns.

3. 'the' can be used before both the singular noun and the plural noun.

Thank you in advance,
All are correct, although #3 sounds like something from a nature documentary.

The lowland gorilla uses "the" before the singular noun, and sometimes, before the plural noun, as a signal to females that he is ready to mate...

There's no difference between #1 and #2. I'd write it the way you have it in #1.
Thanks a lot for your quick response, Grammar Geek!

I got it.

Thanks again,