One who collects coins as hobby :

Philatelist
Ornithologist
Statistician
Numismatist

The correct answer is D. Numismatist.

A numismatist is a person who collects and studies coins, tokens, paper money, and related objects. The word numismatics comes from the Greek words nomisma, meaning “coin,” and logia, meaning “study.”

Numismatists are interested in the history, design, and production of coins. They may also be interested in the economic and social history of the times in which the coins were produced.

Numismatics is a popular hobby and there are many numismatic societies and clubs around the world. There are also many numismatic publications and websites.

A philatelist is a person who collects stamps. An ornithologist is a person who studies birds. A statistician is a person who collects and analyzes data.

I hope this helps!