Concept:Identify the pair where each city has both a seaport and an international airport.
Explanation:Kampala is a landlocked city, so option A is wrong.
Lagos has a major seaport and Murtala Muhammed International Airport.
San Francisco also has a seaport and San Francisco International Airport.
Therefore, option B is correct.
Johannesburg is landlocked, so option C is wrong.
Warri does not have an international airport, so option D is wrong.
Answer:B. Lagos and San Francisco