Final answer:
The equation of the asymptote for the function 2^x is y = 0, which means that none of the provided options are correct.
Step-by-step explanation:
To find the equation of an asymptote for the function 2x, we need to understand the behavior of the function as x approaches infinity or negative infinity. The function 2x is an exponential function, and it has a horizontal asymptote. Specifically, for 2x, as x approaches negative infinity, the function approaches zero. Therefore, the equation of the horizontal asymptote is y = 0, which means that none of the options provided, a) y = 2x, b) y = −2x, c) y = 2x, or d) y = −2x, is correct.