The exhaust pipe of my car has broken.

The Paleogene period was a very important time in the history of the Earth.

I am planning to go to Inner Mongolia, an autonomous region of China, next week.

I have been to Outer Mongolia.

I have been to Chicago.

This is my unused camera.

This old radio uses a cold-cathode tube.

This old radio uses a pentode.

Inside the ear, there are semicircular canals to maintain balance.

This diode only allows current to flow in one direction.