A. Biological oxygen demand (B.O.D.) value of a sewerage sample is always lower than its
chemical oxygen demand (C.O.D.) value
B. Environmental pollution by NOx emission is much higher by four stroke petrol engines as
compared to the two stroke engines
C. Temperature in stratosphere rises with increasing altitude
D. The characteristic of a green house body is that it allows the long wavelength incoming solar
radiation to come in but does not allow the short wavelength infra red radiation to escape out
of the earth’s atmosphere
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