A:1949-1954年
B:1950—1955年
C:1953—1957年
D:1956——1961年
已知椭圆的长轴长是短轴长的3倍,则椭圆的离心率等于( )
I still like those good old songs I often listened to ________________ myself in my spare time.
If you prefer the red evening dress, you'll have to pay _____30 dollars, because it's made of silk.