1 a)Put the metals used (magnesium, copper, iron, zinc)
in order from the least reactive to the most reactive.
The more reactive metal will displace the other metal
from the solution of its metal salt.

Magnesium

  Zinc

 Iron

Copper

Explanation:

The given elements are:

 Magnesium, copper, iron and zinc

 We are to put them in the order from the least reactive to the most reactive of all.

To solve this problem, we simply use the activity series of metals to arrange the elements.

The activity series arranges metals from the most reactive to the least reactive. The more reactive metals displaces the lesser one from solutions.

  So;

      Magnesium

       Zinc

       Iron

       Copper

the answer is either b or c

oxygen, selenium, tellurium, and polonium.

they're all from the same group as sulfur (group 16).