Which question would best promote emergent numeracy development in a two-year-old playing with blocks?

The option that best promotes emergent numeracy development in a two-year-old playing with blocks is the question that encourages the child to count along. By prompting the child to count after you as blocks are put away, it actively engages them in an essential mathematical skill—counting. This interaction not only helps the child practice numerical sequence but also reinforces one-to-one correspondence as they connect the act of counting with the physical objects (blocks) in front of them.

In contrast, while asking a child about their preferences related to the blocks or discussing colors may foster language development and observational skills, they do not specifically target numeracy. Numeracy involves not just recognizing numbers but also developing an understanding of quantity, which the counting activity effectively supports. The question regarding the estimation of the number of blocks could also prompt some numerical thinking, but it may be too abstract for a two-year-old who is still developing foundational math skills.