For function f(x), which condition implies a horizontal asymptote at y = 31?

Limit of f (x) as x approaches 31 = infinity
Limit of f (x) as x approaches infinity = 31
Limit of f (x) as x approaches 31 plus = infinity and Limit of f (x) as x approaches 31 minus = negative infinity
Limit of f (x) as x approaches c plus = 31 andLimit of f (x) as x approaches c minus = 31 for some value of c