The graph of the function $y=a^x$ when $0<a<1$ is

The correct option is C

Graph of $y=a^x$ when $0<a<1$

Graph function should be decreasing function,Means
If there are two different points whose coordinates are $(x_1,y_1)\text{and}(x_2,y_2)$

Such that
$x_2>x_1\text{then}\Rightarrow y_1>y_2$
Hence the correct answer is Option C.