This 5﹣year﹣old boy has such a good sense of d that he never gets lost.
Children will be in danger in a swimming pool if their parents don't take good care of .(they)
The second﹣hand car is much (cheap) than the new one.
This is Mary's (three) time to visit the beautiful city.
Teenagers should learn how to protect (they) from all kinds of dangers.
We are supposed to read (quiet)in the library.