There will be less pollution _____ more people use public transportation.

Every minute is made good ______ of ______for the coming national examinations.

Farmers grow crops either to____their family ___to sell

下面是日常生活中的四个话语情境，在语言表达方面最为得体的一项是（）

It was not until dark ______ he found ______ hethought was the correct way to solve the problem