What fraction of a beam of 7.7-MeV alpha particles incident upon a gold foil 3.0×10-7 m thick is scattered by less than 1°？（）

What fraction of a beam of 7.7-MeV alpha particles incident upon a gold foil 3.0×10-7 m thick is scattered by less than 1°？（）
A.1.35
B.0.67
C.0.05
D.0.84
正确答案：0.84