Question: What is the primary purpose of the `+CVAEACT` AT command in a User Equipment (UE) supporting VAE (Vehicle-to-Everything) layer configuration?
Option 1: To register V2X service identifiers for the UE.
Option 2: To modify the LTE-Uu interface protocol for V2X communication.
Option 3: To query the current status of the VAE layer in the Mobile Terminal (MT).
Option 4: To activate or deactivate the VAE layer support in the MT by performing the V2X service discovery procedure.
Explanation: The `+CVAEACT` command is designed to enable or disable the VAE layer within the Mobile Terminal, accompanied by the V2X service discovery procedure, initializing or shutting down VAE layer functionalities as per relevant specifications, managing the foundational state of VAE layer support for V2X communications over LTE-Uu.