Sentence Correction

This process resulted in a total of 15 new townships: of which, to date, 7 are still in existence.

(a) of which, to date, 7 are still in existence.
(b) of which number, 7 of the 15 are still, to date, in existence.
(c)of the number 15, 7, to date, are still in existence.
(d) to date of these 15, 7 are still in existence.
(e) to date, 7 of the 15 are still in existence

OA is E
What nakes option E stands out. I need an Expert contribution, please. Thanks