15. Primary succession in a forest generally follows which sequence? a. Forest fire; pioneer species; willows; shrubs
b. Abandoned farm; shrubby weeds; cottonwoods; pine trees
c. Flood; mosses; weeds; shrubs
d. Exposed rock; lichens; shrubs; trees

hydrogen is a compound or a single element and a element is a pure substence that cannot be separated into simpler subtances

clorine is a compound its a chemical substance that forms when two or more different elements combine

so both hydrogen and clorine are compounds

multiply it by 5 in order for you to understand i cant give an exact answer.

that's all i luck!