The use of renewable energy helps protect the global environment.

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.

He is a person of strong vanity who reads self-improvement books.

He is the type of person who thinks it's a moonlit night if it's bright, so he only has a one-sided perspective.

He thought deeply and said, 'I think, therefore I am.'

He is facing many difficulties due to gender identity disorder.

Flexibility is necessary for success.

This math problem is based on the principle of additivity.