1. Don't work on the grass.<br />2. It's dangerous to run across the road when the red light is on.<br />3. We mustn't pick the flowers in the park.<br />4. All of us must keep quiet in a library.<br />5. This sign means no smoking.<br />6. Don't draw on the desk. That's the rule of our school.
B. 
C. 
E. 
F. 
