I believe the answer is comparative anatomy. It is the study of the similarities and differences in the structures of different species. Similar body parts may be homologies or analogies, such that both provide evidence of evolution. Similarities in embryos are evidence of common ancestry. For example all vertebrates embryos have gill slits and tails.
We could possibly use water as a fuel source, rather than fossil fuels (which are limited)
Science has already developed something of the sort, and with using water as a fuel source for say vehicles and such, it's inevitable for a positive change to happen because there would be less carbon monoxide; which means less polution.
The answer is males<span> have both an X and a Y </span>chromosome<span>denoted 46,XY.</span>
I think that the numerical expresion for this problem is 17.5
