Refusal to cooperate with a congressional investigation might invoke which citation?

The main hypothesis in the In-Depth section on

Somalia is that: a. the weaker the state, the more individual freedom people have. b. weak states are unable to develop citizens' capabilities effectively. c. strong states are desirable. d. capabilities have deteriorated in Somalis.

The commerce clause of the Constitution

a. gave Congress the authority to regulate commerce with foreign nations and among the several states. b. gave the President sole authority to draft commercial tax legislation. c. prohibited Congress from interfering in interstate commerce. d. provided for a national tariff on the sale of any goods.