How do i combine hydrogen and oxygen?

ixing hydrogen and oxygen equals water, but at room temperature and normal pressure this happens extremely slowly; an energy source, a catalyst, is needed to start the chemical reaction. However, hydrogen is extremely flammable and explodes even in the presence of a lighted match or a spark, so attempting this is not advised.

answer; /// the amount of material dissolved in a measure of liquid(concentration) the above statement is (true); /// good luck