A lake near a village suffered heavy mortality of fishes within a few days. Which of the following statements could be the correct explanation for this ?
(i) Lots of urea and phosphate fertillisers were used in the crops in the nearby fields.
(ii) The croplands of the village were fertillised fields rich in nitrate and phosphate.
(iii) The lake water turned green and stinky.
(iv) Phytoplankton populations in the lake declined initially thereby greatly reducing photosynthesis.

Options

A. a,b
B. a,c
C. b,c
D. c,d

Answer

B