Because an infantry invasion of Japan, would have resulted in <em>Far</em> more casualties for both the americans and the japanese. Than the dropping of an atomic bomb.
Statements C and D are correct.
In America, the development of canals helped lead to the increase in population for several towns/cities that were very seldom settled before. A perfect example of this would be the development of the Erie Canal in New York. Thanks to the Erie Canal, several cities population grew immensely during this time (like Utica, Rochester, and Albany).
Along with this, connecting canals with other waterways made for convenient way of shipping goods and materials. This reduced the cost of shipping goods, making for lower prices for American consumers.
Your answer would be: They wanted to control oil supplies and trade routes in the region.
