(A) In recent years, the rate of cavities has increased in many countries
(B) In some countries, people brush their teeth more frequently than in other countries
(C) The more sugar people eat, the more likely they are to get cavities
(D) In recent years, the consumption of sugar has increased in many countries
The caveat that correlation does not imply causation aside, this shouldn't be particularly difficult; on the other hand, 1 out of 4 Americans believe the sun revolves around the Earth...