题目内容：
Directions: There are 20 blanks in the following passage. For each blank there are four choices marked A, B, C and D on the right side of the paper. You should choose the ONE that best fits into the passage. Then mark the corresponding letter on Answer Sheet 2 with a single line through the centre.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. 1 these wide modern roads are generally 2 and well maintained, with 3 sharp curves and many straight 4 , a direct route is not always the most 5 one. Large highways often pass 6 scenic areas and interesting small towns. Furthermore, these highways generally 7 large urban centres which means that they become crowded with 8 traffic during rush hours, 9 the "fast, direct"way becomes a very slow route.
However, there is 10 always another route to take 11 you are not in a hurry. Not far from the 12 new "super highways”, there are often older, 13 heavily traveled roads which go through the countryside. 14 of these are good two-lane roads; others are uneven roads 15 through the country. These secondary routes may go up steep slopes, along high 16 , or down frightening hillsides to towns 17 in deep valleys. Through. these less direct routes,longer and slower, they generally go to places 18 the air is clean and the scenery is beautiful, and the driver may have a 19 to get a fresh, clean 20 of the world. A．Although
B．Because
C．Since
D．Therefore
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