When new understandings are achieved but the range of information able to be understood does not change, a learner’s zone of proximal development __________.

The zone of proximal development is the gap between what a learner can understand independently and what they can understand with help. If the learner gains new understandings but the upper range of what they can understand stays the same, the gap gets smaller. So the zone of proximal development is smaller, choice C.

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