When a 2kg object is carried from sea level to the top of a high mountain, which statement correctly describes any change in its physical quantities?
a) Its weight remains the same because the amount of matter has not changed.
b) Its mass decreases because the value of g is slightly less at higher altitude.
c) Its weight decreases because the value of g is slightly less at higher altitude.
d) Both mass and weight decrease because gravitational pull is weaker at higher altitude.