Hyperbola: 9x2−y2=1. Line: y=21−αx.
Substituting: x2−9⋅4(1−αx)2=9
⇒(4−9α2)x2+18αx−45=0.
For no intersection (when 4−9α2=0): discriminant <0.
D=324α2+180(4−9α2)<0
⇒−1296α2+720<0⇒α2>95.
∣α∣>35≈0.745.
Among the options, only α=0.8 satisfies this condition.