Sentence Correction (SC) | His studies of ice-polished rocks in his Alpine homeland, far outside

His studies of ice-polished rocks in his Alpine homeland, far outside the range of present-day glaciers, led Louis Agassiz in 1837 to propose the concept of an agein which great ice sheets had existed in now currently temperate areas .

(A) in which great ice sheets had existed in now currently temperate areas
(B) in which great ice sheets existed in what are now temperate areas
(C) when great ice sheets