Which unit provides the means to select vertical and lateral modes as well as speed control?

The Flight Control Unit is the correct choice because it is specifically designed to manage the various modes of aircraft operation, including vertical and lateral navigation modes, as well as speed control. This unit allows pilots to input desired flight parameters and select the appropriate autopilot functions, which play a crucial role in aircraft automation.

By using the Flight Control Unit, pilots can engage and manage different flight modes such as altitude hold, vertical speed, and heading select. This enhances the overall situational awareness and helps ensure a smooth flight by optimizing performance according to operational requirements.

While other units like the MCDU (Multi-function Control Display Unit) and the Primary Flight Display provide valuable information and control capabilities, they do not primarily serve the function of selecting flight modes and controlling speed as directly as the Flight Control Unit does. The Pilot Control Panel also contributes to aircraft operation but is typically oriented more around the direct control of flight systems rather than mode selection.