A, according to the information obtained in one cell of the periodic table of elements, we know that the relative atomic mass of cadmium atom is 112.4, and the unit of relative atomic mass is "1", not "gram", so the option statement is wrong.

b, the symbol "Cd" can represent metal cadmium, a cadmium atom, so the option statement is correct.

c, soluble barium salt, and so on. Cadmium can't make protein lose its physiological activity, so the option statement is wrong. < P > D, the number of cycles is equal to the number of extra-nuclear electron layers of atoms, and the number of extra-nuclear electron layers of cadmium atoms is 5, and cadmium is located in the fifth cycle of the periodic table; The number of protons in the atom = the number of electrons outside the nucleus, 48=2+8+18+18+X, and X=2, so the option statement is wrong. < P > Therefore, B is chosen.