NEW DELHI: The air quality in the national capital showed a marginal improvement on Monday and was recorded in the "poor" category. The city registered a maximum temperature of 31.5 degree Celsius, normal for this time of the year. The capital's 24-hour average air quality index stood at 313 on Sunday, deteriorating from 248 on Saturday.On Monday, the 24-hour average air quality index stood at 263 while...