Which of the following instruments is used for precise placement of sealants?

The micro brush is an essential tool for the precise placement of sealants because it allows for accurate application in hard-to-reach areas and provides excellent control during the sealing process. The small, tapered design of a micro brush helps to evenly distribute the sealant material onto the tooth surface, ensuring that it flows into grooves and pits for maximum coverage and effectiveness.

In contrast, while a plastic instrument can be used for placing certain dental materials, it is generally not as specialized for the nuanced application required for sealants. An articulating paper holder is primarily used to check occlusion and is not relevant to the application of sealants. Burs and bur blocks are involved in cutting or shaping procedures and do not pertain to the placement of sealants either. Thus, the specific design and purpose of the micro brush make it the ideal instrument for this task.