Aprotein in the plasma membrane that binds to specific chemicals in the cell's external environment to regulate processes within the cell is a protein.

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

you should wear a lead protective shield when having teeth x-rays

hope i

-lavira : )

instead of copying and pasting things off of tests or work done on computer which im sure you did, try and read over the question carefully

i think the answer is composed of atoms