Why was the beer purity law or Reinheitsgebot introduced 500 years ago?

On April 23, 1516, the Bavarian dukes Wilhelm IV. and Ludwig X. decreed that “the only ingredients used for the brewing of beer must be barley, hops, and water”. The regulation was called the “Reinheitsgebot” or beer purity law. Breaking this law was punished by confiscation of the offending beverage. 

The law was introduced to (more than one answer is correct):

A) keep undesirable and unhealthy additives out of beer.

B) help producers of hops earn more money.

C) follow the trend to only use as few as possible ingredients as possible.

D) preserve wheat and rye for bread by only using barley for beer.

E) only allow brewers specifically trained by the Bavarian dukes to brew beer.

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The quiz is part of:

• Chemistry Advent Calendar 2016,
  ChemViews Mag. 2016.
  DOI: 10.1002/chemv.201600101