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

This rock is jyamongan, in other words, serpentinite.

This piece of art is made of serpentine.

He is struggling with math problems.

He made a math problem.

He was wearing a kimono with a mon proudly.

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

He is studying at the library every day.

He devoted his life to the study of something.

He excels in every aspect of his job.