America is one of the superpowers in the world.

In physics, ultrashort waves form a part of the electromagnetic spectrum.

He always proactively suggests new ideas.

A healthy diet and moderate exercise help boost immunity.

He is an expert in mechanics.

The Earth maintains its shape due to centrifugal force.

He has a strong ability to get things done to make the project successful.

His imagination is infinite.

This contract takes effect from the date of signature.

He abused that power.