You have to keep on learning if you want to keep ______ with the development of modern science and technology.

A society cannot be successful if it throws tradition away，but it cannot be successful ________ if we do something to stop progress.                                

No matter how much time you spend planning a trip, things still _____ go wrong and air travel is no exception—from weather delays to lost luggage.

(2013·高考浙江卷)As the world’s population continues to grow，the ________ of food becomes more and more of a concern.

I enjoy listening to classical music, but I’m so busy now that I’m not in the _____ for it.