A unitary government gave them too much power to the states
D.
The rest seem wrong.
It could be B though
After Mexico's defeat on the Mexican-American War (1846-1848), the Treaty of Guadalupe Hidalgo came into action. The U.S. was recquired to pay 15 million dollars as compensation for damages, while taking ownership of the territories of California, half of New Mexico, most of Arizona, Nevada, Utah and parts of Wyoming and Colorado.
Mexicans that were settled in these territories, had the choice to relocate within the new limits of their country, or stay and receive American citizenship with full civil rights. This had quite big implications in U.S. culture as it became more racially diverse. In the following censuses between 1850 and 1920 most annexed mexicans were counted as "white", but in reality, segregation only grew with time and continues to do so until this day, with mexican-native americans being considered foreigners almost universally. At the same time, mexican migration to these areas also continued to rise over the years, making the contrast bigger.
Politically, we can say Mexico wasn't in a bad position in terms of their negotiation power. The U.S. had shown itself hesitant to annex Mexico's territories and having deep domestic divisions in regards to the aims and justification for the expansion. However, the military power of the U.S. overshadowed all of that and their victory was definite. The treaty established a pattern of political inequality between the two countries, and this lopsided relationship has stalked Mexican-U.S. relations ever since.
Hope this helps!
