According to the wave mechanical model, an orbital is defined as the
a. most probable location of neutrons
b. circular path for electrons
c. most probable location of electrons
d. circular path for neutrons.

explain your answer in detail.

B. a circular path for electrons . because orbital is a mathematically described region around a nucleus in a atom or molecule that may contain zero , one , or two electrons. 

You know how the first one if filled up like the objects do the same but with the other categories

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.