I believe number 4 is the correct answer
On the one hand, <u><em>your</em></u> is a possessive and means that something belongs or is related to "you", whoever that subject is. On the other hand, <em><u>you're</u></em> is a contraction. It is short for "you are" that includes the personal pronoun <em>you</em> and the conjugated verb <em>to be</em>. Therefore, the sentence that accurately uses the homophones "your" and "you're" is: Don’t forget to pick up your homework before you leave.
The answer is number 3. Hope it helps! :)
B, It's two independent clauses tied together using a conjunction.