URL filtering can block access to websites based on their domain or country code TLDs (e.g., .cn, .ru). This is the correct method to block by location identifiers in URLs.
B). Content filtering blocks based on keywords or categories within websites, not country code.
C). DNS poisoning is an attack, not a control mechanism.
D). MAC filtering restricts devices, not websites.
References (CompTIA Network+ N10-009):
Domain: Network Security - Filtering technologies, URL vs content filtering.