Research has identified a species from the west coast of the United
States which may have been the ancestor of 28 distinct species on the
Hawaiian Islands. What is this species?

The species that research has identified a species from the west coast of the United  States which may have been the ancestor of 28 distinct species on the  Hawaiian Islands.

Is:

The Muir tarweed

Explanation:

Research found that the Muir tarweed, a plant species from the west coast of the united states developed into 28 different species in a process that took it thousands of years. The reason behind this is that different mutations made them change slightly and differentiate themselves from the rest, however, the fertility and their reproduction made them evolve in so many kinds.

me i can you if you would like.

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