Definitely not A or B. It really depends on the size of the boulder... It should be kilograms, unless it's a extremely huge boulder.
1) A The 78g
2) C Push on the wagon in the opposite direction as Jack with a force that is the same as Jack is applying.
Answer:
The magnitude of the force will decrease
Explanation:
The gravitational force is one of the four fundamental forces of nature. It is an attractive force exerted between every object having mass.
Its magnitude is given by the equation:

where
G is the gravitational constant
m1 is the mass of the first object
m2 is the mass of the second object
r is the separation between the objects
As we see from the equation, the magnitude of the gravitational force is inversely proportional to the square of the distance between the objects:

Therefore, this means that as the distance between two bodies increases, the gravitational force will decrease.
Density-Dependent:
1<span><span><span><span>. </span>competition.</span><span>
<span>2. </span>overcrowding.</span><span>
3<span>. </span>predators.</span></span><span>
(These are a few from a test I took, hopefully they help you a bit >.<)</span></span>