What was one important discovery that the Curies made?
A material’s radioactivity cannot be changed by altering the material physically.
A material’s radioactivity can be weakened or intensified by changing it chemically.
Radioactive materials generally contain radium or polonium.
Radioactive materials are found only in the form of salts

the correct option is c.

isotopes refers to different forms of the same element with the same atomic number but different mass number as a result of difference in their neutron numbers. isotopes have different relative atomic mass but share the same chemical properties.

bcde is the incorrect answer it is a

ok whats the question if not i cannot you i need question and need a thing to answer