I would go with C..
A is ambiguous as "they" can refer to both children or linguists.
B alters the meaning by using "one" instead of children
D this sentence ignores the fact that they are analyzing children, not just the pure language
E "their" is ambiguous, could refer to children or linguists
So C must be correct because it clearly refers to children, and although "do" might seem awkward, its necessary in order to make the comparison between children mistakes and the correct forms they use..
yeah i would pick C if i was forced at gun point to pick an answer