Piaget's term for the crucial accomplishment of the sensorimotor stage, at which a child understands that something exists even if it cannot be seen, is .

object permanence

Explanation:

In the year 1936 Jean Piaget,a Psychologists proposed the theory of cognitive development in children. Jean Piaget started this theory after he observed his children behaviour and with this he divided the cognitive development in children into four stages which are given below;

===> sensorimotor stage: from the the time babies are giving birth till they are 2 years old. In the stage, Piaget discussed schemata.

===> Preoperational stage: this stage is from 2 years old to 4 years old.

===> Concrete operational stage: is a stage that occurs between the ages of 7 to 10.

===> Formal operation stage: this is the last stage for cognitive development in children. It occurs from the ages of 11 to adolescence.

answer; (c) all the above