Five-year-old otto complained to his mom that there isn't enough pizza. otto's mom cut the pizza into smaller slices, which delighted otto, who believed that there was now more pizza. otto lacks the concept of:

The correct answer is his lack of conservation. According to the psychologist Jean Piaget, is not present in children during the preoperational stage of their growth at ages 2–7, but develops in the concrete operational stage at ages 7–11.  The action of conserving something, in particular. Conservation denotes to a logical thinking ability. 

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