Graph the given function.
 f(x) = 7^x
 Which key features apply to the graph?
 A. The graph has an asymptote at y = 7 and is increasing as x approaches positive infinity.
 B. The graph has an asymptote at y = 0 and is increasing as x approaches positive infinity.
 C. The graph has an asymptote at y = 0 and is decreasing as x approaches positive infinity.
 D. The graph has an asymptote at y = 7 and is decreasing as x approaches positive infinity.