Final answer:
The term for a single layer of cells where not all cells reach the apical surface is pseudostratified columnar epithelium.
Step-by-step explanation:
The term for a single layer of cells where all cells do not reach the apical surface is known as pseudostratified columnar epithelium. This type of tissue appears to have multiple layers due to the varying positions of the nuclei within the irregularly shaped cells; however, there is only one layer of cells, and not all the cells necessarily reach the apical surface. Unlike other simple epithelium types, pseudostratified epithelium can present the false impression of being stratified.