He decided to focus on the exam.

Tetrose is a monosaccharide with four carbon atoms.

Triose is a type of monosaccharide.

I want to go to Iturup.

He tried to imitate the crowing of a rooster.

I bought a new top.

An albatross is a bird with long wings.

Tetracosane is one of the important compounds in organic chemistry.

This compound is called triacontane and is often used in organic chemistry.

He flatly refused my proposal.