your impression of the GreatWall—Wonderful! Once ____ , it can never beforgotten.

y a meteorological observatory _____ air quality in urban areas from one to five:excellent, fairly good, slightly polluted, poor, and dangerous.

ok is________ boring; it is, in fact,rather exciting and fascinating.

My sister was very afraid all the way because it was the first time she ______ a car. [ ]

Wouldyou like to have_________?—No, thank you. I’ve had enough.