Consider the consecutive reactions: \[A\xrightarrow{k=2\times {{10}^{-5}}{{s}^{-1}}}B\xrightarrow{k=8\times {{10}^{-6}}{{s}^{-1}}}\]\[C\xrightarrow{k=3\times {{10}^{-3}}{{s}^{-1}}}D\] The rate determining step of the reaction is:

• A. \[A\to B\]         
• B. \[C\to D\]
• C. \[B\to C\]                      
• D. \[A\to D\]