sanyalpritish wrote:1. 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[spoiler]（A）[/spoiler]
(E) aperiodic tiles, it turned out to describe

B- is & tiles do not match, work-describes matches
C-work, describing - here describing leaves behind a dangling clause e.g. 'The work of Picasso, describing comtemporary emotions' is an incomplete sentence
D-work does not agree with describe ( should be describes)
also, is so-called a correct usage here? isn't it more negative than ' what are called' ??? Someone please help me identify this subtle difference.
E-it is wrong , no clear referrant? pls help

so only choice left is A

it can refer to either geometry or work

but I am not sure whether the sentence is correct

on the geometry of what are called aperiodic tiles-can any one explain me?