He donated books to the local library.

He donates books to the local school every year.

The government is planning a tax increase for the next fiscal year.

It's difficult to draw his portrait.

Population fluctuations greatly affect the economic situation.

He was taken to the hospital because of peritonitis.

Lemons are rich in citric acid.

Citrate plays an important role in organic chemistry.

The citric acid cycle plays a crucial role in the energy production of cells.

He started a new quest.