The correct answer is: A. Late April to May.
The loo is a hot, dry, dusty wind that blows from the northwest across the Indian subcontinent during the summer months. It is most common in the northern plains, including Bihar. The loo typically blows from late April to May, and can reach speeds of up to 100 kilometers per hour. The wind can cause temperatures to rise to over 40 degrees Celsius, and can make it difficult to breathe. The loo can also cause dehydration and heatstroke, so it is important to stay hydrated and avoid strenuous activity during this time.
Option B is incorrect because the loo typically blows from late April to May, not May to June.
Option C is incorrect because the loo typically blows from late April to May, not late June to July.
Option D is incorrect because the loo typically blows from late April to May, not July to August.