The correct option is A magnetic separation
Magnetic seperation is based on differences in magnetic properties present in ore particles. This method is used to separate magnetic impurities from non-magnetic ores.
FeCrO4 present in the ore is magnetic and attracted by magnet while tin is not attracted by magnet.
On moving over a magnet, FeCrO4 is separated from the tin ore. Hence option (a) is the correct option.