37. She sold her car last year which has been driven for over twenty years.

38 . Thank you very much for sending me a present.

39 . He worked out of the answer quickly, so it was clever of him

40 . Despite being a very busy , contacting her at work is usually quite easy

37. She sold her car last year. She had driven it for over twenty years. (which)

⇒ The car which had been driven for over twenty years was sold last year.

38. You sent me a present. Thank you very much for it. (sending)

⇒ Thank you very much for sending me a present.

39. He worked out the answer quickly. It was clever of him. (so)

⇒ He was so clever that he worked out the answer quickly.

40. Contacting her at work is usually quite easy. She is very busy. (despite)

⇒ Despite the fact that she is very busy, contacting her at work is usually quite easy.