Concept:Tourism is the leading industry when it provides the largest share of a country's income and employment.
Explanation:Among the listed countries, Gambia has a small economy with limited mineral or industrial resources.
Its beaches, climate, and wildlife attract many European visitors, making tourism a major source of foreign exchange.
Tourism supports a large portion of the population through jobs in hotels, transport, and local services.
Therefore, tourism is the leading industry in Gambia.
Ghana relies heavily on gold and cocoa exports.
Liberia depends on iron ore, rubber, and timber.
Nigeria is a major oil-producing country.
In these three countries, tourism is not the dominant industry.
Answer:B. Gambia