In communication one may shift from formal English to informal English or from standard English to non-standard English. This is known as ______.

单项选择题What impressed the author most when he went to watch the lions in the Gir Forest

单项选择题Why are the lions in the Gir Forest especially vulnerable to disease

单项选择题Which of the following is NOT among the reasons that India is creating a secondary sanctuary for the Asiatic lions

单项选择题As can be gathered from the passage, before 1910 the normal running time of a film was probably ______.

单项选择题Griffith's film innovations had a direct effect on all of the following EXCEPT ______.