答案:B
$\begin{array}{cl}
& 0.009~049~999 \\
= & 0.009 \mbox{ (準確至三位小數)}
\end{array}$
$\begin{array}{cl}
& 0.009~049~999 \\
= & 0.009 \mbox{ (準確至三位小數)}
\end{array}$
$\begin{array}{cl}
& 0.009~049~999 \\
= & 0.009~05 \mbox{ (準確至三位有效數字)}
\end{array}$
$\begin{array}{cl}
& 0.009~049~999 \\
= & 0.009~050 \mbox{ (準確至六位小數)}
\end{array}$
$\begin{array}{cl}
& 0.009~049~999 \\
= & 0.009~050~00 \mbox{ (準確至六位有效數字)}
\end{array}$