Which of the following sentences is grammatically correct?

Question

Quizplus · Accepted Answer

This is the only grammatically correct sentence. Its is a third-person singular possessive pronoun, used to indicate that something belongs or relates to a thing, place, or animal that has just been mentioned or whose identity is known. 
Its been four years since I quit smoking.
Its is a third-person singular possessive pronoun, used to indicate that something belongs or relates to a thing, place, or animal that has just been mentioned or whose identity is known. In this sentence, it should be substituted by "it's", the contraction of it is or it has.
Germany is a rich country and it's GDP is the highest of the European Union.
It's is the contraction of it is or it has. In this sentence, it should be substituted by "its", a third-person singular possessive pronoun, used to indicate that something belongs or relates to a thing, place, or animal that has just been mentioned or whose identity is known.
Tell your uncle its time he comes visit: I can't remember the last time I saw him!
Its is a third-person singular possessive pronoun, used to indicate that something belongs or relates to a thing, place, or animal that has just been mentioned or whose identity is known. In this sentence, it should be substituted by "it's", the contraction of it is or it has.

Which of the Following Sentences Is Grammatically Correct