题目内容：
共用题干Highways in the US
The United States is well-known for its network of major highways designed to help a driver get from one
place to another in the shortest possible time.________（51)these wide. modern roads are generally
smooth and well maintained,with__________(52)sharp curves and many straight sections,a direct route
is not always the most__________________(53)one.Large highways often pass_________(54)scenic areas and
interesting small towns.Furthermore,these highways generally_______________(55)large urban centers which
means that they become crowded with_(56)traffic during rush hours,when the"fast,direct"
way becomes a very slow route.However,there is_____________(57)always another route to take if you are not
in a hurry.Not far from the____________(58)new"superhighways",there are often older,________________(59)
heavily traveled roads which go through the countryside._________(60)of these are good two-lane roads;
others are uneven roads ________ (61)through the country.These secondary routes may go up steep
slopes along hilly__________ （62)or down frightening hillsides to towns___________(63)in deep valleys.
Though these are less direct routes,longer and slower,they generally go to places____________(64)the air
is clean and the scenery is beautiful,and the driver may have a chance to get a fresh,clean_____________ （65)
of the world.
_________(64)
A:there
B:when
C:which
D: where
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