1. $I$ asked Mr. Simon, my science teacher, what glass was and $HE$ said that $IT$ is a liquid.
2. Hi Dana! Are $YOU$ still coming shopping with us tomorrow?
3. My mum studied history at university. $SHE$ says $IT$ was a really interesting course.
4. Scientists are working hard to find cures for lots of diseases, but $THEY$ haven't found a cure for the common cold yet.
5. Adam, do $YOU$ think $WE $ should all bring some food with us to your party?
6. Dad, do $YOU$ know if $THEY$ sell computer games in the market?