Ahydrogen fuel cell is more efficient than a combustion reaction because very little of the released energy is released as . when used at home, a fuel cell eliminates the need for because the cell is portable

substitution is the answer in this case

igneous rocks which formed by the crystallization of magma at the surface of the earth called extrusive rocks. they are characterized by fine-grained textures because the rapid cooling at or near the surface did not provide enough time for large crystals to grow.