The correct answer is: B. 300-500 mm.
The Eastern Division of Haryana is a semi-arid region with an average annual rainfall of 300-500 mm. The rainfall is mostly concentrated in the monsoon season (June-September), with the rest of the year being dry. The main crops grown in the region are wheat, rice, and cotton.
Option A is incorrect because the average rainfall of the Eastern Division of Haryana is not less than 100 mm.
Option C is incorrect because the average rainfall of the Eastern Division of Haryana is not more than 700 mm.
Option D is incorrect because the average rainfall of the Eastern Division of Haryana is not more than 900 mm.