Correct the errors in the follow

Correct the errors in the following sentence.
I used to believe that you had to wait exactly an hour after eating. Until you could go in swimming. If you tried to sneak in after only fifty-six minutes. Your stomach would know and you would drown immediately.
【正确答案】：I used to believe that you had to wait exactly an hour after eating ,until you could go in swimming. If you tried to sneak in after only fifty-six minutes , your stomach would know and you would drown immediately.
【题目解析】：p41