[单选题]
The luminosity of th 39(m 9he(k-lztmcu (,xpnm bj9 bj6w m g7 )mzq6i1tipfp9w8oe Sun is $L_⊙$. A main sequence star with twice the radius of the sun and twice the temperature of the sun has a luminosity of $L$. What is the ratio of $\frac{L}{⊙L}$ ?
