Bunuel
The work of mathematician Roger Penrose in the early 1970s, on the geometry of what are called aperiodic tiles, turned out to describe the architecture of a previously unknown class of crystals.
(A) what are called aperiodic tiles, turned out to describe
(B) what is called aperiodic tiles, describes
(C) aperiodic tiles, describing
(D) so-called aperiodic tiles, describe
(E) aperiodic tiles, it turned out to describe
I chose A and this is how I reached that answer.
A lot of people commenting on choice between "what are called" vs "what is called".
I actually started
backwards to choose between
"turned out to describe/describes/describing/it turned out to describe"All 5 answers have different wordings so we can have the clear answer by looking at this part.
First, we need "turned out" because we have to show contrast or expression of surprise.
The sentence suggests that it was originally not expected that this work will describe the architecture of crystals.
So we can eliminate B, C, D.
Second, the part after comma on option E reads that, "it turned out to describe."
"It" here does not have clear antecedent and is redundant since the sentence already has "The work" as the subject.
Eliminate E.
Hence, A is our final answer.