Four atoms of hydrogen combine with one carbon atom to form CH4, but only two hydrogen atoms combine with one oxygen atom to form H2O. Which of the following helps to explain why? More than one answer is correct A Oxygen has two vacancies in its electron shell, but carbon has four vacancies.
B Atoms may share electrons in order to fill their electron shells.
C Hydrogen has one valence electron.
D Metallic bonds form between positively charged metal ions and delocalized electrons.

Mass is the amount of matter in an object.  weight is the measurement of the pull of gravity on an object.  say for example, you travel to the moon which has a different gravitational field compared to the gravitational field of earth. (gravitational fields: earth = 1, moon = 0.165)  now when you are on the moon, the pull of gravity on you is different than on the earth. and as weight is the measurement of the pull of gravity on an object, that means yes, your weight can and will change on the moon.  however, on the moon, on earth or even on jupiter, the amount of mass inside of you remains the same. meaning your physical mass remains constant.  in conclusion it is possible for your weight to change as your mass remains constant.