씁니다->이용합니다 The answer using 씁니다 is wrong. It should answer with 이용합니다.
I was just about to post this.
For anyone wondering:
씁니다 - to use something
이용합니다 - to make use of something
"I use public transportation often" works too.
씁니다 ㅡㅡㅡㅡ탑니다 이용합니다
So, 쓰다 means "write", "wear", and now "use"...
among some dozen more other meanings :)
I am disabling this exercise as it is not conventional to say 쓰다 in this context. 쓰다 is usually with what is under your control that you can manipulate. You may go for 이용하다 instead.