3) I forgot to turn off the lights when I was leaving my house today.
4) I shall never forget seeing the Royal family in London
5) Staying fit means exercising regularly.
6) I am sorry. I did not mean to interrupt your conversation.
7) The children were trying very hard to solve difficult maths problems.
8) Try listening to classical music. It will relax you.
9) Richard stopped studying and turned on the TV.
10) While I was on my way home I stopped to buy some bread.