Answer:
Ca (Calcium)
Step-by-step explanation:
Calcium is a positive ion with a charge of 2+. The metal is also an alkali earth metal since the oxide MO is basic when dissolved in water.
In light of the preceding circumstances;
The metal is not arsenic since arsenic is a metalloid with the oxides As2O3 and As3O5, which are amphoteric (reactive as both, a base and/or acid) and acidic in nature, respectively.
Because it is a metalloid, the metal is not germanium, and even though germanium oxide has the formula GeO2, it is amphoteric.
Because chlorine is a non-metal, the metal is not chlorine.
Because calcium oxide has the formula CaO and calcium is an alkaline earth metal, the metal is unmistakably calcium.
Because selenium is anon-meal and its oxide has the formula Se02 and is acidic, the metal is not selenium.