1. They will show the time machine to the public when they finish it.

- The time machine will be shown to the public when it is finished.

2. He was delighted to receive his aunt’s letter.

- He was delighted that his aunt sent him a letter.

3. Old car tires are recycled to make shoes and sandals.

- People recycle old car tires to make shoes and sandals.

4. I’m very sad that I wasn’t accepted in that group.

- I’m very sad not to be accepted in that group.