John's teacher told him that he needed to cut down on the punctuation; there were commas everywhere in his last essay.

Which sentence is written correctly? a. it's too bad its raining, i wanted too go for a swim. b. its too bad its raining, i wanted to go for a swim. c. it's too bad it's raining, i wanted to go for a swim. d. it's to bad it's raining, i wanted too go for a swim.