Which of these would best describe the structural difference between magnesium and aluminum?
a) magnesium has one more proton than aluminum.
b) magnesium has one less proton than aluminum.
c) magnesium's atomic mass is larger than aluminum's.
d) aluminum has more protons and fewer neutrons than magnesium.

The right answer is B) Magnesium has one less proton than aluminum.  

Magnesium is the chemical element of atomic number 12, Mg symbol.

Magnesium 24 is composed of 12 protons and 12 neutrons. Mg 25 and Mg 26 respectively have 13 and 14 neutrons.

Aluminum is the chemical element of atomic number 13, symbol Al. It belongs to group 13 of the periodic table and to the family of poor metals.

Aluminum 27 is composed of 13 protons and 14 neutrons.

"1. it should be, it has been for about 20 years, and it's really not much different in the end than breeding animals to have particular traits. there are always concerns about genetically engineered animals/plants affecting the environment in unexpected negative ways, but i can't think of an example where the fears didn't turn out to be baseless.  

first, as you point out, it would be a great advance in pharmacology, to be able to tailor drugs and their doses to me. the pros involve better medical treatment. the cons involve privacy issues like insurance companies denying coverage to people with genetic risk factors. looking at dna markers wouldn't affect the frequency of genetic diseases, but it would allow detection of them earlier. and ok, actually i suppose that if people used this information to avoid having children with genetic diseases, some might decrease in frequency."