Q--Is double duty an incorrect phrase for host of Dancing With The Stars?
A--My step-by-step reasoning: Double duty refers to having more than one job at the same time. The host of Dancing WIth The Stars is Tom Bergeron. Tom Bergeron is the host of America's Funniest Home Videos.
So, the answer is no.

Q--Would a person with Anorexia nervosa be more likely to break a bone than a regular person?
A--My step-by-step reasoning: People with Anorexia Nervosa restrict food and as a result lack essential nutrients. Many people with Anorexia Nervosa, are at high risk for osteoporosis(and to a lesser extent bulimia nervosa) will have low bone density and consequently reduced bone strength. People with Anorexia Nervosa, are at high risk for osteoporosis.
So, the answer is yes.

Q--Could Steven Spielberg send emails as a child?
A--My step-by-step reasoning: Steven Spielberg was born in 1946. Email did not become available to the general public until 1995.
So, the answer is no.

Q--Does handedness determine how you use American Sign Language?
A--
My step-by-step reasoning: Your dominant hand typically performs the moving part of a sign in ASL. Your dominant hand determines the hand you use to finger spell in ASL.
So, the answer is yes.