Answer:
D. Negotiations by Louisiana Senator John Slidell put a temporary halt to U.S.-Mexican tensions and hostilities.
Explanation:
It cannot be A because on May 13, 1846 the United States passed an act providing or the Prosecution of the existing war between the United States and Mexico.
It cannot be B because Mexico declared a defensive war against the U.S. on April 23, 1846. Mexico would defend territories, but would not take the offensive.
It cannot be C because "on April 25, 1846, a 2,000-strong Mexican cavalry detachment attacked 70-man U.S. patrol that had been sent into the contested territory north of the Rio Grande and south of the Nueces River." <em>(Wikipedia: Nueces Strip)</em>
It must be D because the rest are true.
