Answer: B. -4
The slope is definitely negative, so you can cross out A and C. The slope of a line is always y/x. If you look at the point (-1,-1,) look up to point (-2,6.)
Comparing the two points I mentioned above, the y difference is 4 while the x difference is 1. This is also -4/1, meaning that the answer is B.
<span>In terms of matter and resources, the Earth is essentially a closed system, because matter and resources are fixed.
</span>In terms of energy, the Earth is an open system, because there is a balanced transfer of energy. (The energy<span> radiates into the </span>Earth's system<span>, from the Sun and</span><span> then it is radiated back into space from the </span>Earth. The<span> flows of energy are regulated by the </span>Earth's<span> atmosphere and ozone layer.)</span>