完形填空(阅读以下材料 回答第51——65题)American RoadsThe United S

完形填空(阅读以下材料，回答第51——65题)

American Roads

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 modem roads are generally_______(52)and well maintained,with_______(53)sharp curves and straight sections,a direct route is not always the most_______(54)one.Large highways often pass _______(55)scenic areas and interesting small towns.Furthermore,these highways generally _______(56)large urban centers,which means that they become crowded with_______(57) traffic during rush hours,_______(58)the"fast,direct"route becomes a very slow route.However,there is almost always another route to take_______(59)you are not in a hurry.Not far from the_______(60)new"superhighways",there are often older,_______(61)heavily traveled roads which go through the countryside._______(62)of these are good two-lane roads; others are uneven roads curving through the country.These secondary routes may go up steep slopes,along high_______(63),or down frightening hillside to towns_______(64)in deep valleys.Through these less direct routes,longer and slower,they generally go to places_______(65)the air is clean and scenery is beautiful,and the driver may have a chance to get a fresh, clean view of the world.

_________(51)

A.Although

B.Since

C.Because

D.Therefore