Only 9 of Delhi's 37 air quality monitoring stations were functioning on Diwali, the Supreme Court was told on Monday. "We don't even know when to implement GRAP (Graded Response Action Plan). That is the severe situation," the court's amicus curiae, Aparajita Singh, said. "Let them (CAQM) answer this question – 'What is the situation of monitoring stations?'" Singh added.