Question

Read these two factual statements about the information contained in the article.

Fact 1: Researchers found more cases of osteosarcoma (one type of bone cancer) than expected. They considered this as uncertain evidence that fluoridated drinking water had the potential to cause cancer in male rats. They did not find similar potential to cause cancer in female rats or in male or female mice.

Fact 2: In 2006, the Harvard study found that in boys, but not in girls, a higher risk of osteosarcoma was linked to exposure to higher levels of fluoride in drinking water.

Which claim can be made using both facts?

Research to determine whether fluoride can cause cancer in humans has not been performed.

It is possible that there is a link between gender and fluoride’s ability to cause certain types of cancer.

Fluoride in the drinking water is safe at any level for humans, but not so for small animals like mice and rats.

Answer 1

"It is possible that there is a link between gender and fluoride’s ability to cause certain types of cancer."

Why: Fact 1 reports a male‑specific finding in rats (increased osteosarcoma in males but not females), and Fact 2 reports a male‑specific association in a human study (boys but not girls). The other two claims are contradicted by the facts: research in humans has been done (Fact 2), and nothing here supports the absolute statement that fluoride is safe at any level for humans.