The correct option is A a description of contrasts
The last line of the passage is "In short, they were born melancholiac, such as make others happy and are themselves helplessly unhappy, creatures of playfulness, charm, and salt tears, of fine fun and everlasting loneliness. ". Very clearly, it consists of contrasting words used in series to describe the two sisters. Therefore, the most obvious answer to the given question is option A) a description of contrasts.