Some vocabulary questions

Hi, I have some questions to ask you.

Is the expression "keep a close eye one somebody" formal? ?

What is the plural of CCTV ?

And do we say that "CCTV has..." or "have..." ?

Thank you.

It's an expression.  So it's neutral.

CCTVs if you are referring to survelliance cameras.  As the name of the Chinese corporation, it can be both singular or plural depending on the context used like words, "government".

Some vocabulary questions.

Hi, I have some questions to ask you.

Is the expression "keep a close eye on somebody" formal?

What is the plural of CCTV?

And do we say that "CCTV has..." or "have..."?

Thank you.

The expression "keep a close eye on somebody" isn't formal. Usually we just say "keep an eye on him" etc without the close.

There is no plural of CCTV. CCTV means closed-circuit television.

I don't quite understand your last question. You can use both "has" and "have".

E.g. Does the casino have CCTV?

E.g. Yes, the casino has state of the art CCTV. 

Some vocabulary questions

Hi, I have some questions to ask you.

Is the expression "keep a close eye on somebody" formal ?  it is used in common speech, and in writing

What is the plural of CCTV ?  haha there is no plural; it is a single entity

And do we say that "CCTV has..." or "have..." ?  has

Thank you.