Answer: BeO
Explanation:
percent by mass of oxygen[tex]=\frac{\text {mass of oxygen}}{\text {Total mass of substance}}\times 100\%[/tex]
percent by mass of oxygen in BeO[tex]=\frac{16g}{25.01g/mol}\times 100=63.97\%[/tex]
percent by mass of oxygen in MgO[tex]=\frac{16g}{40.30g/mol}\times 100=39.70\%[/tex]
percent by mass of oxygen in CaO[tex]=\frac{16g}{56.08g/mol}\times 100=28.53\%[/tex]
percent by mass of oxygen in SrO[tex]=\frac{16g}{103.62g/mol}\times 100=15.44\%[/tex]