Final answer:
Toilet training is typically mastered during toddlerhood, which is from age 1 to 3 years. By the age of three, most children have developed the necessary skills for consistent toilet use. Hence, the answer is B. Toddlers.
Step-by-step explanation:
Toilet training is a significant developmental milestone for young children. According to developmental stages, toddlerhood spans from age 1 to 3 years. During this period, children achieve many growth milestones, including the development of motor skills and language. By age two, toddlers can walk, run, and are often able to use the toilet during waking hours, though complete mastery of toilet training is typically achieved by the end of the toddler stage, around the age of three. This is when most children have sufficient physiological and cognitive development to control their bladder and bowel movements consistently. Therefore, the correct answer to the question is B. Toddlers.