The correct answer is option 1, which is 3-2-4-1. To arrange the hill stations in terms of their height from highest to lowest, we need to consider their elevation from the mean sea level.

Starting with option 1, the order is: Ooty (3), Shimla (2), Darjeeling (4), Mussoorie (1).

Mussoorie is the highest among the given hill stations, followed by Darjeeling, Shimla, and finally Ooty, which is the lowest among the options provided.

Option 2, 3-1-4-2, is incorrect because it places Ooty as the highest, which is incorrect according to the question.

Option 3, 2-3-4-1, is also incorrect because it places Shimla as the highest, which is incorrect according to the question.

Option 4, 2-4-1-3, is incorrect because it places Shimla as the highest and Mussoorie as the lowest, which is incorrect according to the question.

Therefore, the correct order is 3-2-4-1, with Ooty being the lowest and Mussoorie being the highest among the given hill stations.