What is the purpose of teaching the standard language in speech according to the perspective defended by the author? I - To make the understanding...

What is the purpose of teaching the standard language in speech according to the perspective defended by the author?

I - To make the understanding of reading possible.
II - To make the understanding of writing possible.
III - To make the understanding of the standard language possible.
IV - To make the understanding of the regional language possible.
a) Only I and II are correct.
b) Only I and III are correct.
c) Only II and IV are correct.
d) Only III and IV are correct.
e) I, II and III are correct.