Critical Reasoning (CR) | Citing the frequency with which gum disease and heart

First i chose wrong answer.

But now B makes more sense.

Here is my reasoning:

People who brush and floss their teeth regularly are also more likely to exercise and eat a healthy diet.
which means people who DON'T brush and floss regularly (subject to periodental disease) are less likely to exercise and eat a healthy diet. So actually less exercise and healthy diet is causing heart disease and not periodental disease. Alternate cause => WEAKENS

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