Context: With an estimated population of 1,381,069 as of July 1, 2014, San Diego is the eighth-largest city in the United States and second-largest in California. It is part of the San Diego–Tijuana conurbation, the second-largest transborder agglomeration between the US and a bordering country after Detroit–Windsor, with a population of 4,922,723 people. San Diego is the birthplace of California and is known for its mild year-round climate, natural deep-water harbor, extensive beaches, long association with the United States Navy and recent emergence as a healthcare and biotechnology development center.

Question: Which city in Mexico does San Diego border?
Answer: Tijuana

Question: Of all military branches, which one has the strongest presence in San Diego?
Answer: United States Navy

Question: Aside from healthcare, which employment sector has strongly emerged in San Diego?
Answer: biotechnology development

Question: Of the top 10 largest cities in the country, which place does San Diego rank?
Answer: eighth

Question: What is unique about San Diego's harbors?
Answer: deep-water

Question: Which city in Mexico doesn't San Diego border?
Answer: Unanswerable

Question: Of all military branches, which one has the weakest presence in San Diego?
Answer: Unanswerable

Question: Aside from healthcare, which employment sector has weakly emerged in San Diego?
Answer: Unanswerable

Question: Of the top 5 largest cities in the country, which place does San Diego rank?
Answer: Unanswerable

Question: What isn't unique about San Diego's harbors?
Answer: Unanswerable