15. What does this sign mean?

A. Use computers carefully.

B. Be careful with spam in your mailbox.

C. Check your mailbox immediately.

D. Leave your mails in the computer.

16. What does the sign mean?

A. Motorbike isn’t allowed to ride     

B. We can use motorbike here

C. Only motorbike is allowed              

D. Motorbike can’t be stopped