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

Understanding stochastic processes is an important part of statistics.

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

The Markov process is a part of probability theory and is useful for modeling random phenomena.

His role is to fulfill his responsibilities as a leader.

It is important to understand the importance of health.

The cell membrane plays an important role in maintaining the structure of the cell.

The amnion plays an important role in protecting the fetus.

The ophthalmologist diagnosed me with uveitis.

Cats close their nictitating membrane when they are surprised.