UGC NET Environmental Science Q36

Question

In the two sets given below, set-I specifies level in a water sample, while set - II provides observations. Match the two sets and indicate your answer from the code given below.
Set-I (H₂S level in water sample)
(a) No H2S is produced
(b) H2S is produced and is small in quantity
(c) H2S is produced and is medium in quantity
(d) H2S is produced and is high in quantity
Set - II (Observation)
(i) Dark black - high water pollution
(ii) No colour - clean water
(iii) Light black - low water pollution
(iv) Black - moderate water pollution