Which preference assessment allows the observer to record engagement with a single item placed before the individual?

The correct answer highlights a type of preference assessment that involves observing how an individual interacts with a singular item. This method is designed to gauge the individual's interest or preference for the specific item by monitoring their engagement with it over a period of time. The observer places one item in front of the individual, which allows for a focused observation of whether the individual interacts with or engages that item.

In this context, the focus is on examining a single item to assess its attractiveness or reinforcing potential to the individual. This is particularly useful in behavioral assessments, as it allows practitioners to gather information about which items may serve as effective reinforcers based on the individual's level of interaction.

The other types of preference assessments mentioned have different methodologies and objectives. Some involve multiple items at once or do not allow for the same level of isolated observation as the single-item approach, hence their distinction from the correct choice.