Which of the following statement(s) is/are correct? 

• A

  Successive IE's are lower. 

• B

  Less energy is required to remove an electron from a half-filled shell or completely filled shell. 

• C

  ${\mathrm{IE}}_1\text{ of }\mathrm{Al}<{\mathrm{IE}}_1\text{ of }\mathrm{Mg}$

• D

  ${\mathrm{IE}}_1\text{ of }\mathrm{Be}>{\mathrm{IE}}_1\text{ of }\mathrm{B}$