What does the author mean by saying "...the Jews, the Muslims—had lower disease and death

What does the author mean by saying "...the Jews, the Muslims—had lower disease and death rates; which did not always count to their advantage" in Paragraph Four？

A．The zealous religious belief of the Jews and the Muslims delayed their adoption of industrial innovation.

B．The Jews and the Muslims were often accused of conspiracy because their low disease and death rates were seen as suspicious.

C．No washable underclothing was available for the Jews and the Muslims at that time.

D．The Jews and the Muslims had other unhealthy habits despite their cleanliness.

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