There numerous of them but some of them would be contaminated soil which can be followed with altered soil chemistry that contains fewer soil organisms that are essential. The third one would be surface runoff due to extensively modified hydrology of the area.
Answer - D. Were in Search for food to eat.
Reasoning - As ice age and resistant of water became changing in ponds and lake the resource of food started to deplete so evolution became a evolving for creatures aka reptiles.
Genotype of the Q gene is homozygous dominant