The correct options are
A It reflects the sequence of filling the electrons in the order of sub-energy levels s,p,d and f
B It helps to predict the stable valency states of the elements
C It reflects trends in physical and chemical properties of the elements
D It helps to predict the relative ionicity of the bond between any two elements
A) It reflects the sequence of filling the electrons in the order of sub-energy levels s,p,d and f is correct statement as the periodic table is classified into s,p,d & f block elements based on the sequence of filling the electrons in the order of sub-energy levels s,p,d and f respectively.
B) It helps to predict the stable valency states of the elements.is a wrong statement because it cant predict stable valencies.
C) It reflects trends in physical and chemical properties of the elements is a correct statement because they were classified based on the atomic number and successive element's atomic number difference is 1 unit.
C) It helps to predict the relative ionicity of the bond between any two elements is a correct statement,because the compounds of left and right portions of elements in the periodic table are more ionic and middle are covalent.