125.
Sewage containing organic waste should not be disposed in water bodies because it causes major water pollution. Fish in such a polluted water die because of
A
large number of mosquitoes
B
increase in the amount of dissolved oxygen
C
decrease in the amount of dissolved oxygen in water
D
clogging of gills by mud
Answer :
decrease in the amount of dissolved oxygen in water
If the concentration of dissolved oxygen in water is below $$6ppm,$$ the growth of fish gets inhibited.
126.
Consider the following statements regarding compounds which cause global warming. $$'X'$$ is a hydrocarbon, $$'A'$$ and $$'B'$$ are neutral oxides of nitrogen, $$'C'$$ is a blue coloured gas and $$'D'$$ is released when $${H_2}S$$ is reacted with oxygen. Identify the correct statements about $$X, A, B, C$$ and $$D.$$
(i) $$'X'$$ is mainly present in natural gas.
(ii) In $$A$$ and $$B$$ one is diamagnetic and another one is paramagnetic.
(iii) $$'C'$$ can be identified by using liquid element in $$d$$ - block.
(iv) $$'D'$$ causes acid rain.