List two of the procedures that u jerry burger changed in order to replicate the milgram experiment ethically? ?

The experiments that jerry Burger did is almost an exactly the same with Milgrams, but he made two changes to win the approval of the university
First, He stopped the procedures at 150-volt mark (while Milgram stopped the procedure around 450-volt)
Second, Burger made two-step screening process to exclude Individuals that might have negative experience from the experiments 

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C) all of the above hope this