Explanation:

Let's evaluate each statement based on Saskia Sassen’s definition of Global Cities:

- Statement 1: They are centres of direction and policy making for the global economy.

  Explanation: Correct. Sassen argued global cities act as control and command centres in the world economy.

- Statement 2: They are key locations for financial and specialized service firms.

  Explanation: Absolutely right. Global cities attract multinational corporations and advanced producer services.

- Statement 3: They are markets at which the ‘products’ of financial and service industries are bought, sold or otherwise disposed of.

  Explanation: True. These cities operate as important marketplaces for a range of service industry outputs.

- Statement 4: They are characterized by a high level of population density.

  Explanation: ?? Not a defining trait according to Sassen. While many global cities are densely populated, density is not a core criterion in her definition.

Now let’s review the options:

- Option 1: 1, 3 and 4

- Option 2: 2, 3 and 4

- Option 3: 1, 2 and 4

- Option 4: 1, 2 and 3 (Correct – matches the three defining features according to Sassen)

Correct Option:

Option 4: 1, 2 and 3