Which two activities provide the reactants for cellular respiration? releasing air and exercising
breathing in air and exercising
releasing air and eating food
breathing in air and eating food

when atoms of different types of elements join together, they make molecules called compounds. water consists of compound molecules made up of 2 hydrogen atoms and 1 oxygen atom. this is why it's called h2o. water will always have 2 times the number of hydrogen atoms as oxygen atoms.

after receiving a stimus, the sensory receptors send(s) signals to the appropriate area of the body.  

the must be sensory neurons.  

hope its .

sodium i think the chemical element of atomic number 11, a soft silver-white reactive metal of the alkali metal group.

request for reexamination