The correct answer is: Irrigation facilities.
Winter cropping in Manipur is possible in areas with irrigation facilities. This is because the winter months in Manipur are dry, and without irrigation, crops would not be able to grow. Irrigation facilities provide water to crops during the dry season, which allows them to grow and produce a harvest.
The other options are not correct because they do not provide the necessary conditions for winter cropping. High altitude does not necessarily mean that there is enough water for crops to grow. Mild temperatures are necessary for some crops, but not all. Sandy soils can be difficult for crops to grow in, as they do not hold water well.
In conclusion, the correct answer to the question “Winter cropping in Manipur is possible in areas with: Irrigation facilities / High altitude / Mild temperatures / Sandy soils” is Irrigation facilities.