The correct option is C infinite
Equation of hyperbola may be written as,
x21−y24=1
⇒a2=1,b2=4
Now using formula for tangency of a line to a hyperbola c2=a2m2−b2
⇒m2−4=1(m2)−4=m2−4
⇒0=0
So given equation is tangent to the hyperbola for any value of m
Hence, option 'D' is correct.