One Nineteenth-Century Observation, Which Convinced Many of the Existence of at Least

One nineteenth-century observation, which convinced many of the existence of at least plant life on Mars, was the behavior of the polar caps and the dark areas. This means that the:

A) northern polar cap grows during the northern winter while the dark patches in the northern hemisphere turn white, suggesting that they become ice covered.
B) northern polar cap grows during the northern winter while the dark areas in the northern hemisphere begin to radiate in the ultraviolet and infrared.
C) polar caps are connected to each other by a network of canals.
D) dark areas in the northern hemisphere grow during the northern summer as the northern polar cap recedes.