Marie and Pierre Curie Were Working with an Ore That

Marie and Pierre Curie were working with an ore that contained uranium, but found that its radioactivity was higher than could be explained by the uranium in it.What conclusion would be suggested by the method of residues?

A) The ore contained another radioactive element.
B) Uranium is not radioactive.
C) The uranium in the ore was different from other uranium.
D) The ore should be thrown away immediately and all of its residues cleaned up.
E) Radioactivity works differently than the Curies had previously believed.