A child who can stack a maximum of 5 blocks is probably:

A child who can stack a maximum of 5 blocks is likely around the age of 2 years. Developmentally, children typically begin to stack blocks as a form of play and fine motor skill development around their first birthday. By the time they reach 2 years, many can stack about 2 to 4 blocks. Mastering the ability to stack up to 5 blocks usually signifies that a child is honing their coordination and spatial perception, which aligns with 2-year-old developmental milestones.

As children grow older, their stacking ability improves. The ability to stack more blocks, such as 6 or more, becomes typical around age 3. Thus, the ability to stack 5 blocks is a strong indicator of a 2-year-old's fine motor skills and cognitive development.