Gravity largely depends on the comparison of two objects; it's why you have the equation F= (GMm)/r^2. On Earth, you have different altitudes that, with the formula, will give different results for gravity because the radius is different everywhere. This difference on calculations, however, are seen to be miniscule. We know gravity as 9.81 m/s^2 but it might be different by thousandths or hundreds of thousandths of a decimal.
The answer to your question is A
Stable isotopes, radioisotopes, oxygen
longitude and latitude<span />
I think it would be Fusing of 2 or more small atoms into a larger one
