A:阶级性
B:全民性
C:广泛性
D:真实性
-- The boy looks .
-- Yes. Today is his birthday.
在小孔成像问题中,光线穿过小孔,在屏幕上形成倒立的实像,如图所示,若O到AB的距离是18cm,O到CD的距离是6cm,则像CD的长是AB长的( )
—____ do you celebrate the Mid-Autumn Festival?
—We enjoy the full moon and eat moon cakes.