Explanation:

- The passage discusses the worldwide impact of tourism.

- The focus in blank (3) is on the number of countries benefiting from tourism.

- Option 1: "enough" – Incorrect. "Enough" doesn’t logically fit numerically when referring to countries.

- Option 2: "many" – Correct. "Many" accurately conveys that a large number of countries rely on tourism economically.

- Option 3: "less" – Incorrect. "Less" is comparative and doesn’t fit the context of a large countable quantity like countries.

- Option 4: "much" – Incorrect. "Much" is used with uncountable nouns and doesn’t suit the plural form "countries".