Consider the following reasons for the massive fish mortality observed in a lake near a village within a few days:
$(1)$ Excessive use of urea and phosphate fertilizers in nearby crops.
$(2)$ Spraying of $DDT$ using aircraft.
$(3)$ The lake water turned green and foul-smelling.
$(4)$ Initial decrease in phytoplankton in the lake leads to a maximum decrease in photosynthesis.
Which of the above reasons are responsible for the massive fish mortality?

• A
  $1, 3$
• B
  $1, 2$
• C
  $2, 3$
• D
  $3, 4$