9. For the gas reaction of NX₃ with HBr, if X with average molecule weight of 29 and reaction figure shown below. If no air were present in the reaction tube, what will be the ratio (r) of NX₃: HBr gas traveling distances to form the white ring of (. (A) 0.75-0.85 (B) 0.85-0.95 (C) 0.95-1.05 (D) 1.05-1.15 (E) ＞1.15