Final answer:
From the four children described, only the child who exhibits echolalia might warrant further observation by the nurse, as it is somewhat linked to language development, although it is also a usual part of speech for this age group.
Step-by-step explanation:
Among the developmental milestones for 2-year-old children, the ability to stand on one foot is not typically expected until closer to age three or later. A 2-year-old who can build a tower of seven blocks demonstrates advanced fine motor skills for their age, as the norm is six blocks high. Echolalia, or the repetition of words and phrases, is a normal part of language development at this age. Coloring outside the lines is common and appropriate for a 2-year-old, as precision in drawing and coloring usually develops around age four to five. Therefore, none of the described children show immediate cause for concern but the child who exhibits echolalia could be monitored to ensure that this speech pattern evolves appropriately with age.