OE


Extant cells are cells that already exist. The distinction between new cells deriving from extant cells and those cells simply appearing is the main point of this sentence. This sentence clearly makes the comparison. The required word must be a contrast to the idea of cells that "spontaneously appear." Inanimate cells are non-moving cells; it is not clear if these cells exist or spontaneously appear. Neither living, surviving, or mortal, describing the life-state of cells makes a specific contrast to "spontaneously appear."