Just want to share my understanding of why option B is wrong.
- Linguistic pluralism is the only indicator of a nation's diversity.
Say proposition P, Q
P = Linguistic pluralism is the indicator of a nation’s diversity
Q = Other criteria(Say Clothes, Religion) is an indicator of a nation’s diversity.
Focus on this statement, “If this is not an indication of the nation's diversity, nothing else is”.
$\sim P\rightarrow \sim Q$
This is equivalent to $Q\rightarrow P$
So, if other criteria(Say Clothes, Religion) is an indicator of a nation’s diversity then Linguistic is also.
So Linguistic pluralism is not the only indicator of nation’s diversity.