He is a very selfish person.

The culture of our country is highly valued around the world.

It is difficult to find the answer to this big question.

This minor question is too difficult to solve.

I was able to answer all questions correctly.

This classic question is to test whether you are truly a quiz champion or not.

This is really a good problem, isn't it?

He is struggling with math problems.

He made a math problem.

This test had too many malicious questions, making it difficult to solve.