This new mattress has wonderful flexibility.

An airplane can fly in the sky due to lift.

Our country's military power is the strongest in the world.

Our military force is significantly inferior to the enemy's.

Even as he gets older, his virility does not diminish.

The topography of this area was mainly formed by the geomorphic agent of wind.

He is practicing hard to avenge the embarrassment of last year's defeat.

He practiced hard to make up for his previous failure.

How does this machine work?

Please underline this word.