Through careful examination, competent diagnosing and successful treat

The sentence tests parallelism. The marker AND suggests we need a parallel list
and noun- examination - in non-underlined portion suggests we need a list of nouns.
Diagnosing = verb-ing acting as action noun, out since it is not parallel


We need adjective successful to describe more about treatment rather than a conditional statement. Main verb's usage - lead - is also incorrect since
now the intended meaning is distorted.


Same error as A


diagnosis, examination and treatment are now grammatically and logically parallel.
them refers back to physicians, no ambiguity here.


growing without coma incorrectly modifies patients, we need a verb - grow - as in D, not a modifier.