The answer is; D
Inertia is the tendency of an object to resist change to its velocity and direction. The bigger the mass of an object the higher its inertia. In space, the celestial bodies with a bigger mass have more inertia and have a higher gravitation pull (because they bend space-time more than smaller objects). The gravitational force of bigger objects influences on other celestial bodies and beats their inertia force by causing them to change direction and speed.
Probably the answer will be 28.60 because it's a lower number
Research for alternative energy sources have been positively affected, because of other reasons (excluding those EliteAnswers listed), such as:
1) Renewability: This means that resources are replaced as fast as they are used, meaning that they would not run out
2) Cleaner: Most alternative energy would not have the effect of polluting the earth after it is used, and may be easier to clean (if even need to)
hope this helps