`6.` Everybody was astonished by Alice's strange ideas.
`12.` My dog, whose temper is very uncertain, often barks at strangers
`14.` Would you mind helping me to put these chairs away?
`16.` The purse which I lost last week has just been found
`18.`
- Nobody can do this exercise because it is so difficult
- It is impossible for this exercise to be done because it is so difficult
- If this exercise weren't difficult, it would have been done
`19.`
- The house was too cold for her to live in
- It was such a cold house that she couldn't live in
