Which property of the isotopes must be different? A) The atomic number
B) The electric charge
C) The element name
D) The mass number

the atomic number will stay the same no matter how many electrons it has, so it doesn’t decrease nor increase. it’ll only change with a different number of protons

geosphere and hydrosphere.

this is because the geosphere has to do with geological events, while the hydrosphere controls all water on earth.