A non-sandblasted rock could be rough or smooth depending on how it was formed.
A sandblasted rock should be much smoother, since the sand blasts away any rough edges. It will, however, be slightly smaller due to losing those edges.
Atmospheric pressure increases as altitude increases therefore boiling time will need to be extended
A metal rail rusting in damp weather.
It is A. Barium
Explanation: I did that already