Questions 11 to 13 are based on the following passage. At the end of the passage, you will be given 15 seconds to answer the questions. Now listen to the passage.

According to this passage, what is exactly GDP

A．It’s a new method to measure a country’s production.
B．It’s a way to study the economies of different countries.
C．It’s a new system to help make economic decisions.
D．It’s a means to understand a country’s economic changes.