Sentence Correction

Although one link in the chain was demonstrated to be weak, but not sufficiently so to require the recall of the automobile.

A. demonstrated to be weak, but not sufficiently so to require
B. demonstrated as weak, but it was not sufficiently so that it required
C. demonstrably weak, but not sufficiently so to require
D. demonstrably weak, it was not so weak as to require
E. demonstrably weak, it was not weak enough that it required

D

although X, Y... can't use but

and so X as to Y is preferred to enought that...

IMO D -

A - Incorrect Idiom - 'So...as'
B - 'It' should refer a noun, not an action,In this case 'IT' appears to refer the demonstration
C - same as 'A'
D - Good
E - wordy and awkward

IMO - D

yeah

I was looking for "so X as to Y" and only D has it.

Although one link in the chain was demonstrated to be weak, but not sufficiently so to require the recall of the automobile.

A. demonstrated to be weak, but not sufficiently so to require
SENTENCE FRAGMENT
B. demonstrated as weak, but it was not sufficiently so that it required
IT ... IT AFTER BUT IS WRONG
C. demonstrably weak, but not sufficiently so to require
SO AS... MISSING IDIOM
D. demonstrably weak, it was not so weak as to require
CORRECT
E. demonstrably weak, it was not weak enough that it required
IT ..IT..WRONG SECOND IT?REFERES TO WHAT?