Final answer:
Thunderbolt is the interface developed by Apple that combines PCIe and DisplayPort into one serial bus.
Step-by-step explanation:
The interface that combines PCIe and DisplayPort into one serial bus and was developed by Apple is Thunderbolt. Thunderbolt is a high-speed input/output (I/O) technology that allows for the transfer of data and video through a single cable. It offers faster data transfer speeds than USB-C and is commonly used for connecting peripherals such as external storage devices, displays, and audio interfaces to a computer.