The mistakes children make in learning to speak tell linguists more

This is tough . All the opetion with they make it ambigious since they should have a definits antecedent . In this case , it can be children/linguists.
Option C makes it clear however the do after than makes it awkward.
I still go for C.

IMO C

tell linguists more about xyz than do - "more than" and "do" for tell are required here so eliminate A,B, D

between C and E , E uses "thier" which is ambiguous, does not clearly refer to children, hence C is clear answer.

Bumping for review and further discussion*.

*New project from GMAT Club!!! Check HERE

GMATNinja would you mind explaining how what is "do" referring to here?

than do

The mistakes children make in learning to speak tell linguists more about how children learn language than do the correct forms they use.

"Than do" means "than the correct forms tell linguists about how children learn language".

@SD1713-

Yes, the role of "do" associates with "learn." The meaning is expressing that linguists have two ways to tell how children learn a language.

1. mistakes children make
2. the correct forms they use

The sentence is clearly conveying that linguists learn more from the mistakes children make than they do/learn from the correct forms used by children.

The use of "do" brings much-needed clarity!

Cheers!
Stacey

I think, the question is all about the meaning.
Scrapping all non - essential elements, we can deduce the intended meaning - mistakes tell linguists more than correct forms. i.e.

The linguists are interested in learning how children learn a language. While learning language, children will make mistakes and will also use correct forms.
Linguists don't get much help when children use the correct form; however, linguists get greater help when children use incorrect forms, make a mistake.
So, crude sentence can be written as -
mistakes help linguists more than the correct forms do.

which can be written in reverse as -
mistakes help linguists more than do the correct forms.

Now, let's articulate the sentence with non - essentials (underlined) that we removed earlier, we get -
The mistakes children make in learning to speak help (tell) linguists more about how they learn language than do the correct forms they use.

The only problem remaining is the ambiguous "they" which can refer to both linguists and children. Let's remove the by simply using "children" again. So, we get correct sentence:

The mistakes children make in learning to speak tell linguists more about how children learn language than do the correct forms they use.


Answer: C

Hope it helps.
Cheers

Here's the official explanation provided by the GMAC for this question:

The sentence, as presented, is open to multiple interpretations. By far the most plausible one is that the author intends to draw a contrast between the extent to which one type of observation tells linguists about children’s language learning and the extent to which another type of observation tells linguists about that same topic. The meaning can be effectively communicated by using a parallel structure between verb phrases: tell linguists more about ... than do, in which the pro-verb do serves as a concise substitute for tell linguists ... about.

Option A: This is ambiguous. It could mean either (1) the mistakes tell linguists more about how children learn language than the correct forms tell them about that topic or (2) the mistakes tell linguists more about how children learn language than they tell about the correct forms children use. The plural noun most immediately preceding the pronoun they is linguists rather than children. This could make the pronoun appear, hypothetically, to refer to the linguists, so it would be better to repeat children instead of using the pronoun.

Option B: This has the same ambiguity that answer choice A has.

Option C: Correct. Here, the correct forms they use is prefaced with the verb do, which functions in this context as a pro-verb having tell linguists as its antecedent. This makes it clear that the mistakes tell linguists more than the correct forms tell them. Repeating children instead of using a pronoun removes any apparent doubt about whose language learning this is referring to.

Option D: This has the same ambiguity that answer choice A has. Learning language is also unclear–it could be interpreted as meaning how to learn language rather than how language is learned.

Option E: Although there is little doubt that their means the children’s, the structure makes this technically vulnerable to an uncharitable or joking interpretation according to which their has linguists as its antecedent. For greater formal precision, it would be better to clarify this by saying the children’s instead of their.

The correct answer is C.

Please note that I'm not the author of this explanation. I'm just posting it here since I believe it can help the community.

It can be solved easily if you just choose an option in which "they" is not used since it can't have clear antecedent between linguists and children. Further, if you think which two entities are being compared, in this case "the mistakes" and "the correct forms", then pretty easily option C stands out.