Hello.

I have a few grammar questions.
1)would you use "police" or "the police" in the context: "police are taking strict measures agains illegal immigration"?
2)which aricle is better in "they were listening to the/a traditional Christmas message" "he delivered a/the Christmas message"(or does it depend on the context?)
3)are the articles correct in the phrases "all Catholics (no article)" "the Catholics of the whole world" "Catholics in the whole world"
3)is it possible to say "of all the world"?
4)which structure is correct: "he expects the assistant to prepare / to have prepared all the documents by 6 o'clock"?
Thank you very much for your help.

1. Either one works; I'd use "The police..."

2. If there is only one Christmas message, then use "the," but if you are listening to one of several, then use "a."

3. Yes, correct.

3. It looks right, but it really depends on the entire sentence that phrase is in.

4. Both work OK, but I'd use the first one.