It's difficult to write an essay on this topic.

I achieved a big success.

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

Would you like to observe the stars at the observatory tonight?

She was thinking with her hand on her forehead.

There are five questions on the test.

His calligraphy theme expresses the beauty of nature.

He asked me three questions.

He threw a difficult question at me.

This problem is difficult.