题目

Runners in a relay race pass a stick in one direction. However, merchants passed silk, gold, fruit, and glass along the Silk Road in more than one direction. They earned their living by travelling the famous Silk Road. The Silk Road was not a simple trading network. It passed through thousands of cities and towns. It started from eastern China, across Central Asia and the Middle East, and ended in the Mediterranean Sea. It was used from about 200B.C to about A.D. 1300, when sea travel offered new routes. It was sometimes called the world’s longest highway. However, Silk Road was made up of m下列四个命题中，正确的是（ ）A.经过一点，有且只有一条直线与这条直线平行B.同旁内角相等，两直线平行C.相等的角是对顶角D.在同一平面内，过一点有且只有一条直线与已知直线垂直