"Tobacco Plants Are Grown in Soils with High-Phosphate Fertilizers That $\alpha$

"Tobacco plants are grown in soils with high-phosphate fertilizers that are naturally contaminated with the alpha-particle emitting radionuclide polonium-210.In one year, the average smoker will irradiate the bronchial epithelium with 8 to 9 rem, the equivalent dose of radiation from 250 to 300 chest X-ray films per year" Pediatrics, September 1993, p.464) .How many sieverts is equivalent to 8.5 rem for $\alpha$ particle emission? RBE for $\alpha$ particles =20)

A) 43 Sv
B) 0.0043 Sv
C) 1.7 Sv
D) 0.085 Sv
E) 85 Sv