While Hans Holbein the Younger is most often identified with his English portraits, scholars have long been recognizing him as a superb draftsman and a remarkably versatile artist and who was fundamental in synthesizing the novelties of the Italian Renaissance with the rational tradition of Northern Europe.
(A) been recognizing him as a superb draftsman and a remarkably versatile artist and who "Recognize" is a one time activity - once "recognized", there is no need to keep repeating it. Incorrect use of present continuous tense "been recognizing" - simple past would suffice ("long..."). Also, "a superb draftsman..." and "who was fundamental..." are not parallel. Eliminate.
(B) been recognizing him for being a superb draftsman and a remarkably versatile artist and he Same errors as in (A). Also, "a superb draftsman..." and "he was fundamental..." are not parallel. Eliminate.
(C) recognized him as a superb draftsman and a remarkably versatile artist who Correct answer - above errors have been rectified and no new errors are introduced.
(D) recognized him as a superb draftsman and a remarkably versatile artist and he Same parallelism error as in (B). Eliminate.
(E) recognized him for being a superb draftsman and a remarkably versatile artist and who Same parallelism error as in (A). Eliminate.