Agents such as barium sulfate and iodine, which can be administered orally, rectally, intravenously, or in an artery to enhance the real-time imaging of dynamic processes in blood vessels, or peristalsis in the gi tract are called agents.

Radiocontrast agents are substances such as barium sulfate and iodine administered to a patient to improve the real time imaging of dynamic processes in blood vessels, or peristalsis in the gastro intestinal tract. These agents work by absorbing external X-rays that cause low exposure on the X-ray detector.

a time line cause it goes from 685 to 978

i'm thinking (a) to keep sand in place; ////////////

explanation: a sand fence or sandbreak, like a snow fence, is used to force windblown, drifting sand to accumulate in a desired place. sand fences are employed to control erosion, sand dune stabilization, keep sand off roadways, and to recruit new material in desert areas.