Carbon dioxide is one of the main causes of global warming.

This factory is emitting a large amount of sulfur dioxide.

I eat lunch at twelve o'clock.

This diode only allows current to flow in one direction.

My younger sister is twenty-one years old.

I hurried down the lower two steps.

Kenjiro is my best friend.

Keijiro is my best friend.

He was working abroad for twelve months.

I learned the meaning of 'ichi ni ten' in the classical Japanese class.