The United States is well-known for its network of major highways designed to help a drive
However, there is almost always another route to take【56】you are not in a hurry. Not far from the【57】new "super highways", there are often older, less heavily traveled roads which go through the countryside. 【58】of these are good two-lane roads; others are uneven roads curling through the country. These secondary routes may go up steep slopes, along high cliffs, or down frightening hillsides to towns【59】in deep valleys. Through these less direct routes, longer and slower, they generally go to place where the air is clean and the scenery is beautiful, and the driver may have a【60】to get a fresh, clean view of the world.
(51)
A.Although
B.Since
C.Because
D.Therefore