Beth normally breast-feeds her baby; however, during the workday beth's mother watches her baby, and the baby must be fed with a bottle. beth has noticed that her baby's approach to being bottle-fed is somewhat different than when the baby is being breast-fed. piaget would say that this is an example of

The answer to this question is Substage 1: simple reflexes of the sensorimotor stage.
This stage usually happens when the children enter the age period of 0 - 1.5 years. In this stage, the children only capable to involuntary response towards certain stimuli (such as start to suck everything that they put in their mouth, as a biological programming to obtain food)