Which of the following steps should be involved in an experiment to prepare copper(II) sulphate crystals?
A. adding excess CuCl2(s) to H2SO4(aq)
B. adding CuCl2(s) to excess H2SO4(aq)
C. adding excess CuO(s) to H2SO4(aq)
D. adding CuO(s) to excess H2SO4(aq)