Which of the following statements is true? a.) Cool air is less dense than warm air.
b.) Electricity flows from positive to negative areas.
c.) Sound does not require a medium for travel.
d.) Magnetism is caused by the spinning motion of electrons.

Duchenne muscular dystrophy is a serious condition caused by a recessive allele of a gene on the human x chromosome. the patients have muscles that weaken over time because they have absent or decreased dystrophin, a muscle protein. they rarely live past their twenties. how likely is it for a woman to have this condition? a) women can never have this condition. b) one-fourth of the daughters of an affected man would have this condition. c) one-half of the daughters of an affected father and a carrier mother could have this condition. d) only if a woman is xxx could she have this condition.