His smile has an irresistible charm.

I think this situation is unavoidable.

Since the train was stopped, I had no choice but to use a taxi.

He likes to take a walk in the park at dusk.

Linear programming is a part of operations research and is used to find the optimal solution.

Paying the urban planning tax is a citizen's duty.

The United Nations Environment Programme is providing solutions to global environmental problems.

In response to his actions, I felt anger and showed an inevitable reaction.

He had a narrow escape in that accident.

Unable to bear the pain, he had no choice but to scream.