15. What does the sign mean?

A. Be alert! There’re pedestrians crossing in front of library.           

B. Be careful! There’re walkers nearby.                    

C. All vehicles must stop because of the walkers.    

D. No one is allowed to cross the road.

16. What does the sign mean?

A. The airbag is activated.

B. The airbag isn’t working.

C. The airbag needs to be serviced.

D. Engage the airbag right now.