The correct answer is: D. no article
The reason is that "London" is a proper noun, which is a noun that refers to a specific person, place, or thing. Proper nouns are always capitalized and do not take an article.
Here are some examples of other proper nouns:
- The United States of America
- The Eiffel Tower
- The Great Wall of China
- The Pacific Ocean
- The Amazon River
As you can see, all of these nouns are capitalized and do not take an article.
I hope this helps! Let me know if you have any other questions.
