The Element Mercury Causes Massive Brain Dysfunction, Including Hallucinations and Delusions

The element mercury causes massive brain dysfunction, including hallucinations and delusions. A "silver filling" from your dentist is actually 50% to 66% mercury and only 35% silver. The American Dentistry Association (ADA) says that "silver amalgams" are safe. A psychologist wishes to determine whether mercury fillings affect a child's brain functioning. The Coolidge Personality and Neuropsychological Inventory Neuropsychological Dysfunction (ND) scale has 20 questions, such as "My child has learning problems," "My child is hyperactive," and so on. The overall score on the ND scale ranges from 0 (no evidence of brain dysfunction) to 20 (severe brain dysfunction) . The survey is given to parents as they visit a dentist with their child. The number of "silver" fillings is noted, as is the child's gender. For analysis purposes, the children are divided up into whether they have no fillings, one to three fillings, or more than five fillings, and their ND score is noted.
-The degrees of freedom for gender are

A) 1
B) 2
C) 42
D) 47