Answer:
The sentence which should be rewritten is the first one.
A revised version should read as follows:
The term "It's not over until the robust lady sings" comes from the opera Der Ring des Nibelungen.
Explanation:
A bias is a prejudice or preconception in favor of or against one a group of persons or an individual, especially in a way considered to be discriminatory.
There are two biases found in the excerpt. One is directed at the opera and the other at the singer.
Faced with the decision of resolving one of both, it is safest to use a word that is euphemistic in the description of the subject - the lady.
The key offensive word there is "fat".
Politically, it is a more forgivable option to resolve in contrast with focusing on removing the bias on the opera which was described as <em>a painfully long solo.</em>
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Cheers
