[Orgmode] Controlling float position in LaTeX export

[Manish]

Hello,

A figure is exported to LaTeX with markup like below.

,----
| \begin{figure}[htb]
| \centerline{\includegraphics[scale=0.8]{./time-series.png}}
| \caption{\label{fig:bt}Weekly Business Transaction over Past Two Years}
| \end{figure}
`----

How can I replace [htb] with [H] (during the export itself?)  It is
required by "float" package to ensure that floats appear where I want
them to appear.  Is there an option that controls that?

Thanks,
-- 
Manish