Answer: b. Senator John Slidell, José Herrera
Step-by-step explanation:
In the prelude to the Mexican - American War which cane after the US annexation of Texas, President Polk appointed Senator John Slidell as U.S. Minister to Mexico after hearing that the Herrera administration preferred to negotiate than to fight.
When Slidell arrived though, the President José Herrera government which was facing pressure at home for perceived weakness refused to meet with him and discuss the Rio Grande border dispute as well as the sale of California.