Read the following sentences: “In recent years, there has also been a gradual shift toward more ecologically conscious agricultural practices. Societies around the world have begun to feel the devastating effects of decades of unsustainable agricultural practices and deforestation, and many have started taking preventative measures.”
As used in the passage, what does the word “unsustainable” mean?

A. dangerous to farmers
B. not able to be maintained
C. very important
D. unhealthy to animals