All synthetic materials ultimately come from

Factories-i.e. created from humans

Explanation:

Synthetic materials, like polyester, nylon and acrylic, don't exist naturally but are made in factories. Synthetics are created through an industrial manufacturing process in which petroleum, a fossil fuel, is extracted from the earth and mechanically transformed into fibers for clothing.

blood enters the heart through two large veins, the inferior and superior vena cava, emptying oxygen-poor blood from the body into the right atrium of the heart. as the ventricle contracts, blood leaves the heart through the pulmonic valve, into the pulmonary artery and to the lungs where it is oxygenated.

d. organisms have cells with different shapes and functions.