For the first question regarding the cause of the Mexican-American War, the correct answer is:
b. The United States annexed Texas.
The annexation of Texas by the United States in 1845 was one of the key factors that led to the war, as it increased tensions between the U.S. and Mexico.
For the second question regarding the result of the Mexican-American War, the correct answer is:
d. It gave the United States territory known as the Mexican Cession.
The Mexican Cession included a large portion of territory that the U.S. acquired from Mexico as a result of the war, including present-day California, Nevada, Utah, and parts of Arizona, New Mexico, Colorado, and Wyoming.