I want to learn more about the American political system, but I don't know where to get the ________ . 

“Why couldn’t they meet us at five o’clock?” “Because they were delayed by ________.”

She bought the painting at a much higher______ than its real_______.

It’s obvious that his ______ to the problem is wrong, so we’d better try another way to solve it.

With international ______ and education exchanges increasing every year, the number of Chinese students studying abroad has increased rapidly.