He knew that cholera would never be controlled _____ its cause was found.

You'd better not leave the medicine ________ kids can get at it.

_____ private cars are bringing us convenience, they may also cause more traffic accidents and pollution.

_____ news came ______ Dolly died of a terrible disease.

_____ the government recovers the vehicle purchase tax and the oil prices go up continuously, the sales of the vehicle in China are still increasing every year.