The most abundant of all of the isotopes of an element will be the one who's mass the mass of element is closest to. In this case, the mass of atomic carbon is closest to the mass of carbon-12.
Thus, Carbon-12 is the most abundant isotope.
Well, it was to capture Japanese controlled islands until the Japanese came into range of the American Bombers, which was different from them going after the Japanese and invading the islands.
