Yes because it is the teacher's outing but since there are more than one teacher it has to be posessive and plural so its teachers' outing.
Yes it is correct to say "Have a wonderful Holiday."
Yes it is.
You should say for your convenience it is *gramatically correct-*just means correct
Yes.
Yes, there is a verb and and a noun and they are in the same tense therefore it is gramatically correct.
That's not even a complete sentence. The words TO, SAT, THIS, PEOPLE and IS can not be combined in any way to make a grammatically correct sentence. ------------------------------------------------------------------------------------------------------------- Assuming the question should be Is it gramatically correct to say, "This people is..."? then it is not correct. One should say, "These people are...".
No, it is not grammatically correct. The correct form would be "Why would you worry instead of being happy?"
I don't see why not although beginning a sentence with 'or' is unusual.
No. It would be better to just say those or these.
Yes. "She has no idea that you are even here." is a correctly formed, gramatically correct sentence.
No. You would normally say something like higher up.
No. I would say: "You and her will begin to ship the product".