I think its salinity because the other things have something to do with tracking precipitation
Covalent Bonds hold together atoms within a molecule
<span>No they don't,they have to work together for an organ to function.</span>
They produce oxygen they are used as shelter, they are used for blocking the shade, they sustain other animals that sustain the planet and us.
The answer should be NEURONES (nerve cells).
Neurons transmit electrical signals called NERVE IMPULSES from the cell body through the axon to the end plate. The junction between the end plate and the adjacent cell is called SYNAPSE. impulses passes through the synapse by diffusion of chemicals.