How do scientists know that the k-t extinction took place

Reformers worked to change schools by making them more:

Plz ! after the first battle of bull run general ivan mc dowell was removed from command of the union army he was replaced by a. general ulysses s. grant. b. general george mcclellan. c. general robert e lee. d. general george meade.

Brainliesttt !me : ) describe the responses to terrorism in the united states.