31. They will install solar panels on the roof of our house next week.-> Solar panels ...........................................................................................................................32. There were some trees in the field, but now there aren’t any.-> There used ......................................................................................................................33. What is the distance between Hanoi and HCM city? -> How far ……....................………….....……………………………………………..?.34. People invented the wheel thousands of years ago.-> The wheel ............................................................................................................................35. Although she eats lots of food, she is still very slim.->In spite of ……………………………………………………………...............................