What type of hydraulic units support the aircraft on the ground and absorb landing shock?

The correct answer relates to the role of shock struts in supporting the aircraft on the ground and absorbing landing shock. Shock struts are specifically designed as part of the landing gear system and use hydraulic fluid in conjunction with gas to dampen the impact forces experienced when the aircraft lands.

These struts work by compressing and expanding, allowing for the dissipation of forces that would otherwise transfer directly to the fuselage, which helps to maintain structural integrity and passenger comfort. When the aircraft lands, the shock struts compress, utilizing hydraulic pressure to manage the landing impact and rebound smoothly back into their original position, providing ongoing support during ground operations.

Other options like landing gear actuators, while part of the landing gear system, primarily deal with the extension and retraction of the gear rather than absorbing landing shock. Self-contained hydraulic units are generally used for various hydraulic applications on the aircraft, not exclusively for shock absorption related to landing forces. Pressure sensors, on the other hand, are used to monitor pressure levels within hydraulic systems and do not directly contribute to shock absorption or support.