B. Soil Contamination
All the other answers are talking about clean and pure things while this answer is the only negative one. So B is your answer.
secondary succesion takes place
Independent variable: Temperature
Levels: Room temperature
Freezing point 0C
Boiling point 100C
Dependent variable: breaking point of rubber bands measured in certain amount of temperature
Because it carries a lot of blood to the arteries
I think this information may be help you
The plants in a specific environment be impacted if there was a sudden drop in the amount of bacteria present in that area, there are positive and negative consequences associated with this situation.
Positive:
The decrease in bacterial colonization will prevent the plant from the diseases caused by the bacteria and this will promote plant growth. Like, black rot in Brassica caused by Xanthomonas campestris, bacterial canker in tomato, capsicum and chilli caused by Clavibacter michiganesis.
Negative:
Plants remains in symbiotic relationship with bacteria in order to obtain impermeable inorganic minerals from the soil. In the absence of bacteria, the plants will not receive these nutrients, and their growth may be hampered. Example bacteria fixes atmospheric nitrogen which is taken up by the root nodules of leguminous plants. In return these bacteria gets the food like carbohydrates produce by the plants
