Final answer:
In the Class I cavity preparation on tooth 1.5 (maxillary right second premolar), mesiopulpal, buccopulpal, and linguopulpal line angles are present. The axiopulpal line angle is not a term commonly used in cavity preparations, so it would not be present, making option D the correct answer.
Step-by-step explanation:
The question pertains to dental anatomy and the specific cavity preparations for tooth treatments. A Class I cavity preparation is one that involves the pits and fissures on the occlusal, buccal and lingual surfaces of molars and premolars, as well as the lingual surfaces of incisors and canines when there is caries present.
In the context of a Class I cavity preparation on tooth 1.5, which is the maxillary right second premolar, a mesiopulpal line angle would indeed be present, as this refers to the angle formed by the junction of the mesial and the pulpal wall surfaces within the tooth. Similarly, buccopulpal and linguopulpal line angles, named for their respective locations (buccal and lingual surfaces) joining with the pulp chamber, will be present in a cavity preparation.
However, the axiopulpal line angle is not a term commonly used to describe a specific line angle within Class I cavity preparations, hence option D, axiopulpal, would be the line angle not present in Class I cavity preparations on tooth 1.5.