The function $$y=a\times 2^{}x$$ is constant when $$a=$$~\uline{~~~~~~~~~~}~, the function $$y=2\times b^{}x$$ is constant when $$b=$$~\uline{~~~~~~~~~~}~. 
选项为:A:1,1  B:-1,-1  C:0,1  D:0,-1  请回答其中一个选项.