Soil erosion occurs a. where animals eat away all the plants c. on steep slopes b. when forests are removed d. all of the above

the dark variety, as they are not visible on the dark tree barks

explanation:

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