Answer:
c.O
Explanation:
From the periodic table:
Ionization energy tends to increase from IE6 → IE7 drastically at 13329 to 71345. Hence, from this process, we can infer that the removal of electrons takes place from the inner shell which in turn has a higher affinity for the nucleus. This must be oxygen because oxygen contains 6 valence electrons. The removal of this valence electron after the sixth ionization results in the achievement of a stable nearest Noble gas configuration. Hence, the rapid change in the ionization is obvious from IE6 to IE7.
Thus, the element that relates to the IE trend is oxygen.
The awnser to your question would be B
The ionic compound is CaSO4
1.) MgO + Fe --> FeO + Mg
2.) H + I --> HI
3.) Na + I --> NaI
4.) NaO + H2O --> NaOH + H