Final answer:
The landing gear of an aircraft can be fixed, manual, hydraulic, or electric, depending on the type of aircraft and its design.
Step-by-step explanation:
The landing gear of an aircraft can be fixed, manual, hydraulic, or electric, depending on the type of aircraft and its design. Fixed landing gear is permanently attached and does not retract, while manual landing gear requires the pilot to manually operate a lever or crank to retract or extend the gear. Hydraulic landing gear uses hydraulic fluid and a hydraulic system to retract and extend the gear, and electric landing gear uses an electric motor to operate the gear.