I think the answer is:
B. Chemical Change.
Atomic mass is just protons plus neutrons
Bonjeur monseur, la french are here! it seems you have a problem with the elements on earth. lead seems correct since it is indeed a harmful material
Weight of the balloon = 2.0 g
Six weights each of mass 30.0 g is added to the balloon.
Total mass of the balloon = 2.0 g + 6*30.0 g = 182 g
Density of salt water = 1.02 g/mL
Calculating the volume from mass and density:

Converting the volume from mL to cubic cm:

Assuming the balloon to be a sphere,
Volume of the sphere =
π

r = 3.49 cm
Radius of the balloon = 3.49 cm
Diameter of the balloon = 2 r = 2*3.49 cm = 6.98cm