The observed results of an experiment that occur from changes in the independent variable are known as a. controlled variables b. dependent variables c. trials d. constants

Dependant variable as it is what is measured

i think that is new experiments yield untrustworthy data and should be carefully considered, because you don't know what will happen with the experiments.

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