Which of the following milestones is expected in a typical 3-year-old's development?

The milestone of building a tower of 6 blocks is expected for a typical 3-year-old's development as this age group shows significant improvement in fine motor skills and hand-eye coordination. At around 3 years, children can manipulate small objects more skillfully, allowing them to stack blocks effectively. This activity demonstrates their ability to plan and execute sequences, which is a growing aspect of their cognitive and motor development.

In contrast, hopping on one foot typically develops a bit later, usually around age 4. Children might begin to demonstrate this skill at 3, but it is not fully expected. Using sentences with 7 or more words is usually seen in older children, generally around age 4 or 5, as they expand their vocabulary and syntactic complexity. Skipping with alternating feet is a more advanced gross motor skill that is typically expected around age 5 or 6, as it requires more coordination and strength than what is generally seen in 3-year-olds.