The carbonyl group plays an important role in organic chemistry.

The foundation of this building is very strong.

Ki is my best friend.

The base of this building is very strong.

He continued to search to find the origin.

There are three pyramids in Egypt.

This plan was made based on facts.

The foundation stone of this building was laid 100 years ago.

Compounds containing acyl groups play an important role in organic chemistry.

The allyl group plays an important role in organic chemistry.