He devoted his life to the study of something.

He is studying at the library every day.

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

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 in the middle of actual production of artistic works.

Yusaku is my best friend.