In the Old Testament, what specific action did God instruct Moses to perform so the Israelites could overcome the Amalekites, and what was the immediate result?

A Raise his staff; the Israelites prevailed as long as it was raised. B Pray aloud; the Israelites gained ground with each prayer. C Circumcise all the men; they were emboldened by the covenant. D Sacrifice a lamb; the Amalekites were struck with fear.