An exponential function is graphed in the xy‑plane. If the graph of the function is always decreasing and has a y‑intercept of 20, which of the following could be the function's equation?
A) y=−20(1.75)​^x​​
B) y=20(1.75)^x
C) y=-20(0.75)^x
D) y=20(0.75)^x