We should recycle to prevent environmental pollution.

Have you ever had an indirect kiss with him?

A gap is created in the wall of the building due to the earthquake.

He made time to meet his friends by squeezing it into gaps in his busy schedule.

A gap gradually developed between him and me.

The White House is the official residence of the President of the United States.

He has an absolute pitch, so his musical talent is very high.

In organic chemistry, cyclodecane is a cyclic saturated hydrocarbon consisting of ten carbon atoms.

In this chemical reaction, cyclooctadecane is the main product.

Pentadecane is produced in this chemical reaction.