Mrs. Weston asks Colin if he wants his sandwich in one piece, or cut into two pieces. Colin asks her to keep it in one piece, because he isn't hungry enough to eat two pieces. Colin's answer suggests that he:

does not yet understand conservation

Explanation:

The concept of conservation was proposed by psychologist Jean Piaget and the concept emphasizes that an infant recognizes that altering the shape of a material or object does not alter its number, total volume or mass. His hypothesis indicates that this capacity is not present in children between the ages of 2 and 7 but comes later at the concrete operational stage between the ages of 7 and 11. As per the question, Colin does not understand that pieces of sandwich would not decrease its size and it reflects that he lacks the understanding of conservation.

the branch of biology that deals with the normal functions of living organisms and their parts.

the way in which a living organism or bodily part functions.