Final answer:
A toddler employing a gross motor skill could be engaging in activities like running, climbing, or walking stairs. These skills involve the large muscles and are seen in milestones achieved by the ages of two and three, where toddlers refine their abilities to walk, run, and climb more competently.
Step-by-step explanation:
Among the toddlers practicing different skills, a toddler employing a gross motor skill would be the one engaged in activities such as running, climbing, or walking up stairs. Gross motor skills refer to the abilities required to control the large muscles of the body for walking, running, sitting, crawling, and other activities of similar nature. For example, by the age of two years, toddlers can typically run and walk up and down stairs on both feet, one step at a time, which is a display of their developing gross motor abilities. By the age of three, these skills are more refined, allowing them to climb stairs one foot per step and to engage in more complex activities like climbing.
Considering the developmental milestones provided, Toddler A might be employing gross motor skills if they are climbing or mastering stairs without assistance, Toddler B if they are running (even though they may fall often), Toddler C if they are walking up and down stairs on their own, and Toddler D if they are engaged in any of these activities or additional gross motor skills such as jumping or playing with a ball by rolling or tossing it.