According to the extract, what is the alternative that cont...

According to the extract, what is the alternative that contains the right explanation about the gerund in bold type?

“Swimming is an amazing exercise. It’s healthy, fun, relaxing and a low-impact sport. I know this from personal experience. Last year while I was jogging I injured my left knee. I don’t go jogging anymore, now I’m considering joining a swimming competition.”

The gerund is: