關於mass同weight一問

A is correct. B is incorrect.
For A, weight = mass X acceleration due to gravity
i.e. W = mg
where g is the acceleration due to gravity (gravitationalfield strength), in which it can be treated as a constant.
So, weight of an object at a particular place isproportional to its mass.
For B, mass is a property of matter. That is it does not varyin different places. It should be the same at all places.
Weight is a property of space. W = mg, The weight depends onthe magnitude of g, which can be varied. So it varies very slightly atdifferent places.

you may ask,
why the manitude of g can be varied? (statement2)
因為地球不停地轉動，會產生一種自轉離心力，因此物體所受重力的大小，等於地心引力和自轉慣性離心力的合力，應當是地心引力減去自轉慣性離心力在垂直方向的分量。因為地球是兩極稍扁的橢球體，越近赤道，地面與地心的距離越遠，地心引力也就越小。另一方面，越近赤道，物體隨地球自轉產生的自轉離心力卻越來越大，所以越近赤道，物體實際所受重力就越小
參考資料：十萬個為甚麼—物理篇1(p.2)
上述資料涉及中六課程，不過這本書是不分年級的-.-