Vehicles often come into conflict with other vehicles and pedestrians when their intended courses of travel intersect (交叉),and end up being in each other' s way. The general principle that establishes who has the right to go first is called “right of way”，or “priority”. It determines who has the right to use the conflicting part of the road and who has to wait. Signs, signals, markings and other features are often used to make priority clear.
A driver must yield (it) the right of way to other drivers:
• When approaching a YIELD sign. Slow down or stop to avoid a crash.
• Even after the light turns green when there are vehicles in the intersection.
• When approaching emergency vehicles using sounding or flashing sirens.
• After coming to a complete stop at an intersection where there is a stop sign or a flashing red signal. If there is no stop line, stop before the crosswalk.
• When making a left turn on a red light after a stop from a one-way street to another one-way street with traffic moving to the left. (See Figure A. )
• When two vehicles on different roadways arrive at a four-way stop intersection at the same time, the vehicle should yield to the vehicle on its right. (See Figure B.)
• When coming out of an alley, building, private road or driveway after coming to a complete stop. (See Figure C.)
• When crossing traffic at the end of a“T” road with no traffic control signs or signals. (See Figure D.)
21. What’ s the purpose of the text?
A. To explain the law of right of way.
B. To illustrate traffic signs and signals.
C. To inform drivers of general traffic rules.
D. To introduce traffic rules to pedestrians.
22. Which is the right behavior according to the text?
A. Drive on once the light turns green.
B. Keep driving if there is no stop line.
C. Yield to emergency vehicles at any time.
D. Slow down when approaching a YIELD sign.
23. Which of the following description is TRUE according to the figures?
A. Figure A: B should yield to A.
B. Figure B: A should yield to B.
C. Figure C: A should yield to B.
D. Figure D: A should yield to B.