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He is majoring in chemistry at university.

He is an expert in chemistry.

He received the letter challenging him to a duel and began preparing for the duel.

Gender roles are an important element in defining individual behavior in society.

His role is to fulfill his responsibilities as a leader.

Her smile was shining brightly.

His name is Sansan.

Organic solvents play an important role in chemical reactions.

It is important to understand the importance of health.