Concept: The final festival observed by the Israelites in Egypt was the Passover, which marked their deliverance.Explanation:The Israelites celebrated the Passover on the night before the Exodus, eating the lamb with unleavened bread and bitter herbs.That same night, the Lord struck the firstborn of Egypt, and Pharaoh allowed Israel to leave.No other festival is recorded as being celebrated right before their departure.Answer: B. Passover