A:1:1
B:2:1
C:3:1
D:1:3
— Mr. Smith. He is one of _______teachers in our school.
△ABC与△A′B′C′是位似图形,且△ABC与△A′B′C′的位似比是1:2,已知△ABC的面积是3,则△A′B′C′的面积是 ____