Which of the following statements about the effects of agricultural techniques on the environment is true?
a.
fertilizer used for agriculture can enter bodies of water, causing eventual oxygen depletion.
b.
pesticides and herbicides are potentially harmful to bodies of water only before they degrade.
c.
agricultural practices have limited impact on the surrounding environment.
d.
tillage is an important agricultural practice that has no known environmental impact.

a. Fertilizers used for agriculture, can enter bodies of water, causing eventual depeletion of oxygen.

Explanation:

Fertilizers are the chemical or biological substances which are used to improve the quality of the nutrient deficient soil. Although these susbtances improves the plant growth but when these substances enter into water they can cause eutrophication. Eutrophication is a natural phenomena in which water is occupied with minerals and essential elements present in the fertilizers which results in the growth and abundance of plants in the water body. This results in the decrease in levels of oxygen in the water body which results in decline of the aquatic species. Eutrophication is an environmental hazard resulted due to agricultural practice.