What department of the u. s. government was led by kirstjen nielsen

Department of Homeland Security

Explanation:

Nielsen was the Secretary of the Department of Homeland Security until early 2019, when she resigned over differences with President Trump in how to execute America's immigration policy.

would not cooperate with each other voluntarily.

answer; /// i do believe that the correct answer is (a); a farming tribe that settled primarily along the mississippi and arkansas rivers;