A train car is to a train, as a is to a polymer as a molecule is to a .

The correct answer is - Polymer (macromolecules), monomer (building blocks

Explanation:

Polymers are comparable to the train as polymers are made up of several monomers linked together to carry more but can be removed from the polymer if required similarly the train cars that are comparable to the monomers or building block are joined together but can be taken off.

Macromolecules are polymers that are made up of joining monomers together and makes large molecules. Macromolecules like carbohydrates are made up of monosaccharides as monomers, proteins are made up of amino acids as monomer or building block, lipids are made up of fatty acids and nucleic acid are made up of nucleotides.

the oceanic zone is typically defined as the area of the ocean lying beyond the continental shelf, but operationally is often referred to as beginning where the water depths drop to below 100 meters (328 feet), seaward from the coast to the open ocean.

explanation:

cells use diffusion to get substances in and out of themselves. that diffusion will occur across the cell membrane or the outer covering of the cell. because we are talking about the surface of the cell, surface area and volume are  important factors here. as a cell increases in size, its surface area and volume increase as well.  we call that the surface area to volume ratio (sa: vol).  but the catch is that  volume increases at a greater rate than surface  area. in other words, as a cell gets bigger, the sa: vol gets smaller. so a really small cell like bacteria is mostly cell membrane (surface) with very little contents (volume). a really big cell like an egg, is mostly insides with a super thin membrane. so what ends up happening is that the cell cannot efficiently diffuse all of the stuff it needs in/out to survive. therefore cell size is limited to about 100mm. so how do we make organisms bigger than 100mm? cells divide! by dividing and becoming multicellular, organisms are able to grow!   check out the diagrams i attached to see the effect of sa: vol. i hope this ! good luck!