Why Did God Instruct Moses to Have Every Israelite Family

Why did God instruct Moses to have every Israelite family sacrifice a lamb and paint their doorframes with its blood?

A) so the angel of death would not visit those houses a.
B) so the Pharaoh would be afraid to send his soldiers to those houses for fear of infection
C) to show the world how the Jews suffer
D) as a symbolic offering to the Pharaoh