B.
B is the most logical answer. brain readiness, they are infants, self-explanatory, so is independence. Motor skills are the most logical BUT it depends on what kind. Gross motor skills are what toddlers do, crawl, jump, skip, roll around etc. Fine motor skills are what we do first like moving our feet, fingers, eyes, arms, legs, etc.
I learned this raising my siblings and cousins throughout my life.
Though I could always be wrong with answer B.