Which equation is the exponential regression equation? (* = multiplication)

a) y=1.042^x
b) y=3.807+1.042^x
c) y=1.042*3.807^x
d) y=3.807*1.042^x

Which term below correctly completes the following sentence? if a function has a vertical asymptote at a certain x value, then the function is what at that value