1¡¢The airport__________(complete) next year will help promote tourism in this area.

2¡¢_____________ (work out) the difficult maths problem, I have consulted Professor Russell several times.

3¡¢—Why not eat this cheese up?

—The doctor advised me to go on a diet __________(get) rid of my extra weight.

4¡¢The doctors are busy doing what they can     ____________(save) the dying man.

5¡¢She could no longer find a way _________(get) into the valley.

6¡¢___________ the convenience of digital payment, many senior citizens started to use smart phones.

A. To enjoy         B. Enjoying         C. To have enjoyed  D. Enjoy