Hydrogen sulfide is the foul-smelling gas that gives rotten eggs their unpleasant odor.
(Hydrogen sulfide; is; the foul-smelling gas that gives rotten eggs their unpleasant odor) (foul; smelling; gas that gives rotten eggs their unpleasant odor) (the foul-smelling gas; gives; rotten eggs; their unpleasant odor)
Hydrogen sulfide foul the foul-smelling gas
is smelling gives
the foul-smelling gas that gives rotten eggs their unpleasant odor
gas that gives rotten eggs their unpleasant odor
rotten eggs their unpleasant odor