The correct answer is: a) These descriptions of nature symbolize freedom and possibility in Mrs. Mallard's life and perhaps an "awakening" from her grief or her repressed life as a married woman. These images also suggest that Mrs. Mallard's yearning for freedom is something natural.
Indeed, the description mentions the “tree tops aquiver with new life”. This is a beautiful example of the pathetic fallacy, since the blossoming of nature in spring is associated with Mrs. Mallard’s awakened emotions before the possibilities of freedom. She is also quivering due to the emotional turmoil associated to her realization. The fact that spring is traditionally associated with the renewal of life after the death of winter means that the symbolism here is used to express the fact that a new life awaits Mrs. Mallard.
Furthermore, the sky is more of less gray with several “patches of blue”. This of course brings attention to the fact that her life is momentarily gray with the death of her husband but that it is gradually opening up to sunnier, blue skies of personal freedom.