Answer:
4
Step-by-step explanation:
4 because it cant be 2 because even though it has a comma it is still a run on sentence just like 3 because they are two separate phrases and should be separated by a semi colon, however that is not a choice. While 1 clearly separates each phrase with a period it still doesn't seem to make a complete sentence. 4 on the other hand clearly shows a complete sentence while connecting the two phrases with "so". This makes it were they are not separate phrases. Two other things that could separate them are a semi colon and the word and.