"I am living on a hill."
Translation:Tá mé i mo chónaí ar chnoc.
In the “Mark a̲l̲l̲ correct translations” variant of this exercise, both Tá mé … and Táim … were offered. I checked both of them, and both were recognized as being correct; thus, Táim … seems to be accepted now (2016-07-25).
Because of the preposition ar.
ar is a bit unusual, in that it can cause lenition, eclipsis or no initial mutation at all. The entry for ar in the FGB says:
(In references of a general nature it does not normally affect initial letter of following noun, e.g. ar muir, ar cíos, ar cosa in airde, "on sea", "rented", "galloping". In qualified or particularized references it lenites, e.g. ar mhuir na beatha, ar chíos mór, "on the sea of life", "at a high rent". Eclipses in a few instances, e.g. ar gcúl, "backwards")
This is a "particularized reference", so chnoc is lenited.