Graphite's lubricant nature in moon

$\begin{array}{1 1}(a)\;Increases&(b)\;Decreases\\(c)\;Remains\;same&(d)\;Invalid\;question\end{array}$

Lubricant nature depends not only in the sillipage between the planes,but also on a film of moisture or gas molecules absorbed on the surface of graphite layers.Dry graphite in vaccum is not slippery.
Hence (b) is the correct answer.