Which actions are part of a system of methodical tests and refinements specific to technological design?

Which of the following is always a reactant in a combustion reaction? oxygen nitrogen hydrogen carbon

The characteristics of two different types of reactions are shown below: reaction a: electrons are gained by the atoms of an element. reaction b: protons are lost by the atom of an element. which statement is true about the atoms of the elements that participate in the two reactions? their identity changes in both reaction a and reaction b. their identity changes in reaction a but not in reaction b. their identity changes in reaction b but not in reaction a. their identity remains the same in both reaction a and reaction b.

Which is the most concentratic acid