Two balls of same material and finish have their diameters in the ratio of 2 : 1 and both are heated to same temperature and allowed to cool by radiation. Rate of cooling by big ball as compared to smaller one will be in the ratio of____________________?
A. 1 :1
B. 2: 1
C. 1 : 2
D. 4 : 1
E. 1 : 4