The crystal structure of an ionic compound depends on the . a) sizes of cations and anions. b) ratio of cations to anions. c) masses of cations and anion. d) both a and b

The crystal structure of an ionic compound depends on the sizes of cations and anions, as well as the ratio of cations to anions. The ratio of the cations and anions need to be even, otherwise, the crystal won't form.
 
So the answer would be D, both A and B. 

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. 

answer: mole of the gas

answer: mole of the gasexplanation:

answer: mole of the gasexplanation: this is because 1 mole of a gas is 22.4dm³, which is use in ideal gas