Final answer:
b) Needle displacement is the most common cause of extravasation, which is when liquid leaks out of a vessel into the surrounding tissue, while increased blood flow is responsible for the redness associated with inflammation.
Step-by-step explanation:
The most common cause of extravasation is needle displacement. Extravasation occurs when there is an accidental leakage of a liquid from a vessel into the tissue surrounding it. This typically happens in a medical setting when drugs are administered intravenously and the needle becomes dislodged, allowing the medication to leak into the surrounding tissue.
As for the question on the redness of inflammation, the increased redness associated with inflammation is due to increased blood flow to the affected area. This is a response to the inflammatory processes that dilate blood vessels, allowing more blood to reach the inflamed tissue, thereby causing redness.