Which correctly fixes the error in the sentence?

I couldn't go to the party; because I had a big test the next day.
I couldn't go to the party; I had a big test the next day.
I couldn't go to the party I had; a big test the next day.
I couldn't go to the party, I had a big test the next day.

Question

Which correctly fixes the error in the sentence?

I couldn't go to the party; because I had a big test the next day.
 I couldn't go to the party; I had a big test the next day.
 I couldn't go to the party I had; a big test the next day.
 I couldn't go to the party, I had a big test the next day.

Mercury · Answer

major hint: a semicolon can be inserted between two independent clauses to punctuate them