Which one of the following is a way to establish the discovery of a new language?

The passage clearly states that 'Only after a considerable period of contact does it transpire that the speech is so different that it has to be considered a different language.' This indicates that establishing contact over a period of time with the speakers is essential to determine that a new language has been discovered. Finding similarities actually leads to misclassifying it as a dialect, and comparing with lingua franca is what delays discovery.