Which ones of the following statements are true? If y = f(x) has a horizontal asymptote y = 1, then for every a in the domain f(x) = 1. y = arctan(z) has two horizontal asymptotes y = and y=- y = f(x)=121x +212 +11 has a unique horizontal asymptote y = 22 x = 11 and 2 = -11 are vertical asymptotes of y = f(x)=e4-121, y = f(x) = # +11 has two horizontal asymptotes y 1 and y = -1. 21 y = 1 is the horizontal asymptote of y = f(x) = e -121.