If you change the subscripts it would change the reactants or products and then you would be solving a different formula, you would change what the chemical is
The answer is
D. Covalent bond
Hope this helps you have a great day.
B. Share Electrons.
Hope this helps.
This is more of a physics explanation, but here we go.
Mass is a measure of how much "matter" is in an object. Weight is the force applied onto an object by gravity. Weight itself can be related to mass like this:

where g is a gravitational constant. For our purposes, it's defined by whatever planet you are on. Following this, we can demonstrate that mass is NOT the same thing as weight if we take two objects of the same mass and put them on different planets.
Let E refer to Earth and F refer to Mars

Following this, we can see clearly that weight is not the same as mass:

If weight was the same thing as mass, the two values would be the same, as the mass of the two objects is the same. But since weight is defined in the context of gravity, they are not.