Well without a description om shooting in the dark. But id assume that the answer is Trench Warfare. Since A- was around since contact with Native Americans and largely popular in North America. B- Only was used and discovered in WW2. And C- was used but was largely frowned upon and condemned by both sides.<span />
Balance of power between the federal and state governments
Hope this helped :)
<span>This is of course somewhat of a subjective question, but in general most would agree that in general expansion was not justifiable since the Mexicans and Natives were doing nothing to provoke the US. One could argue it was justifiable since Americans needed more land. </span>
Any women who could read or write would be able to be trained as a physician.