下列各句，没有语病的一句是（　　）

If Greeks and Turks had not helped each other after the earthquakes five years ago,they____ mortal enemies instead of friendly neighbors later on..

derstandings_____ from lack of social communication, unless _____ with properly, may leadto serious problems.

I remember _________the factory owed a small workshop and two machines.

Children under 12 years of age in that country _____ be under adult supervision when in a public library. [ ]