Pls help I am confused my sister got me sweating

Consider the four elements above. which one of these elements will combine with oxygen in a 1: 1 ratio?

The content of manganese (mn) in steel was determined spectrophotometrically and with the use of the standard addition method. an unknown sample of mn from a digested steel sample gave an absorbance of 0.185 when analyzed spectrophotometrically. when 5.00 ml of solution containing 95.5 ppm mn was added to 50.0 ml of the unknown steel solution (digested sample), the absorbance was 0.248. calculate the concentration, in parts-per-million (ppm), of mn in the digested steel sample solution.

What changes occur in the reaction indicated by the equation? check all that apply. the hydrogen nucleus loses protons. the oxygen nucleus gains protons. the bond in h2 is broken, and new bonds are formed between hydrogen and oxygen atoms. each electron associated with a hydrogen atom is shared with an oxygen atom.