1. It was surprising for me to learn that he is the only child in his family.
I was …….
2. I was sitting on a chair. It suddenly collapsed.
The chair
3. You should take a map because you might get lost in these mountains.
In case
4. Don’t litter the place around you or it will be a junk yard.
– If..

I was surprised to learn that he is the only child in his family
2)The chair on which I was sitting suddenly collapsed
3)in case you get lost in these mountains, you should take a map
4.If you litter the place around you, it will be a iunk yard.