From OG pg. 746 #120.

A �rm that specializes in the analysis of handwriting
claims from a one-page writing sample that it can
assess more than 300 personality traits, including
enthusiasm, imagination, and ambition.

(A) from a one-page writing sample that it can
assess
(B) from a one-page writing sample it has the ability
of assessing
(C) the ability, from a one-page writing sample,
of assessing
(D) to be able, from a one-page writing sample,
to assess
(E) being able to assess, from a one-page writing
sample

Correct answer is
D

More Spoiler:
My question is on the usage of commas. Sentence D correctly uses the idiom, "claim + infinitive." But what happens if we removed the commas surrounding "from...sample"? For example, the new sentence would be:

A firm that specializes in the analysis of handwriting claims to be able from a one page writing sample to assess more than 400 personality traits...

I am assuming this is wrong now because by removing the commas, "from...sample" become a restricted prepositional phrase. Since it is restricted, the idiom, "claims to be able to" is no longer valid. Is this correct? Do rules regarding idioms always hold true when idioms have a non restrictive clause or prepositional phrase sandwiched between them? For example,

A firm that specializes in the analysis of handwriting claims, from a one page writing sample, that it can assess more than 400 personality traits.

Would the sentence above be correct too?