The zinc in a copper-plated penny will dissolve in hydrochloric acid if the copper coating is filed down in several spots (so that the hydrochloric acid can get to the zinc). The reaction between the acid and the zinc is: 2H+(aq)+Zn(s)→H2(g)+Zn2+(aq).
When the zinc in a certain penny dissolves, the total volume of gas collected over water at 25 ∘C was 0.961 L at a total pressure of 748 mmHg .

A penny dissolves in hydrochloric acid if the copper coating is filed down in several spot... ... When The Zinc In A Certain Penny Dissolves, The Total Volume Of Gas ... is filed down in several spots (so that the hydrochloric acid can reach the zinc). The reaction between the acid and the zinc 2H+(aq)+Zn(s)→H2(g)+Zn2+(aq) .

im not exactly sure but i think its b!

it means there are 3 atoms of oxygen