【单选题】

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

Now listen to the passage.
Which is NOT the mentioned result of the change of the way of livingA．They learnt to live together peacefully.
B．They learnt to help one another when in neeD、
C．They learnt to fight against common enemies with joint efforts.
D．They learnt to invent more things to make life easier.