Your incorrect answers were 3 and 4.
For number 3, the correct answer is b. This is because not language is not necessarily oral (i.e. there are written languages).
For number 4, the correct answer is b. Although comparative linguistics is a branch of historical linguistics, comparative linguistics is specifically concerned with comparing the linguistics of one person/place from the next.
Fact= something that can be proven to be true
opinion= what someone thinks of something that is not true to everyone
I think the answer is “C”