Ascientist formed a theory based on an experiment he conducted. many years later, researchers studied his experiment to see if there were any possible sources of error. should the researchers do this?

The researches could review his experiments and all of his theories to detect any possible flaws. 

It has to be b i hope this

The activity series is shown in the attached picture. if the element is below the other, then you can displace the other. following the activity series as a guide, the reactions are as follows: nickel and aluminum chloride3 ni + 2 alcl₃  → 3 nicl₂ + 2 albarium and copper bromideba + cubr  →  no reaction because cu is less oxidizable than bapotassium nitrate and aluminum3 kno₃ + al  → al(no₃)₃ + 3 ksodium phosphate and zincnaso₄ + zn  → znso₄ + na