Question

this metal is important in the production of steel and also in helping blood vessels transfer oxygen to body tissue. radon lithium nickel iron

Explanation:

Iron is a key component in steel - making. In the human body, iron is part of hemoglobin in red - blood cells, which helps blood vessels transfer oxygen to body tissue. Radon is a radioactive gas, lithium is used in batteries among other things, and nickel is used in alloys but not for oxygen - transfer in the body as described.

Answer:

D. iron