The Emperor Augustus, it appears, commissioned an idealized sculpture

The verbs are and calls indicate that the sculpture is being viewed and judged in the present.

Thus, neither the past tense verb constituted (in B) nor the present perfect verb have constituted (in C) is correct; both suggest that the statue’s features once constituted an artificial face but no longer do so.

Also, B would be better if that were inserted after so unrealistic, although the omission of that is not ungrammatical.

Choices D and E use unidiomatic constructions with enough: unrealistic enough to constitute would be idiomatic, but the use of enough is imprecise and awkward in this context.

Choice A, which uses the clear, concise, and idiomatic construction so unrealistic as to constitute, is best.

https://www.nytimes.com/1984/01/10/science/scholar-detectives-learn-how-augustus-idealized-his-image.html

THE Emperor Augustus, it seems, had trouble with his image - and he fixed it just as many a polititian would today: with good public relations.

An idealized vision might well have persisted today had it not been for the recent detective work of archeologists and scholars, especially in West Germany, about the way Rome's first Emperor is shown in the more than 200 ancient sculptural portraits of him that have survived.

The researchers have concluded that around 27 B.C. the Emperor commissioned a model portrait head whose features were far more serene and ideal than those he bore in life. The adopted son of Julius Caesar, Augustus was born in 63 B.C., became sole ruler in 31 B.C., at the age of 32, and reigned until his death at 77, in A.D. 14.

Copies of Idealized Face

Faithful copies of this idealized prototype, they say, were made available for further copying by sculptors in Rome and elsewhere, and copies of it, and copies of copies, make up the majority of the surviving portraits.

In the sculptures of this variety, often called the Prima Porta type after a statue discovered at Prima Porta, just outside Rome, the features are so unrealistic as to constitute an ''artificial face,'' according to Paul Zanker, director of the University of Munich's Institute of Classical Archeology. Professor Zanker's remarks, given in a lecture last summer, were published later last year in Forschung (Research), a journal published by the West German Institute for Research.