He couldn't walk because the sole of his foot hurt.

He sang the song in falsetto.

Can you teach me the trick of this game?

He strongly supported the imperial reverence theory.

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

This room has high humidity.

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.

His actions left ruin for his family.