Refer to figure.
A pressurisation system regulates the cabin altitude by balancing the bleed air supply to the cabin against the air exhausted through one or more outflow valves located in the fuselage. 

In normal automatic operation, the cabin pressure controller (CPC) commands the position of the outflow valves according to a pre selected schedule (cabin altitude target, rate of climb or descent, landing field elevation). 

If the automatic controller fails, the crew switches to the manual mode and takes direct control of the outflow valve position with a dedicated cockpit selector or knob. By opening the outflow valve more, the cabin altitude rises (the cabin depressurises), by closing it more, the cabin altitude decreases (the cabin pressurises). The two safety valves (positive pressure relief valve and negative pressure relief valve) are pure mechanical protection devices that open automatically when the maximum positive differential is exceeded or when the cabin pressure becomes lower than the outside pressure; they are not pilot controlled in manual mode. 

Positive pressure safety valve → INCORRECT. The positive pressure relief valve is a mechanical safety device that opens automatically if the cabin to outside differential exceeds the maximum allowed (typically about 9 psi on most transport aircraft). It is not commanded by the pilot, neither in automatic nor in manual pressurisation mode. Its function is purely protective.

Negative pressure safety valve → INCORRECT. The negative pressure relief valve opens automatically when the cabin pressure becomes lower than the outside pressure (for example, on rapid descent), letting outside air flow into the cabin to prevent structural damage. Like the positive valve, it is a mechanical safety device, not a pilot controlled element.

Outflow valve → CORRECT. The outflow valve is the active regulating element of the pressurisation system. In automatic mode, its position is commanded by the cabin pressure controller. When the controller fails and manual mode is selected, the pilot directly commands the position of the outflow valve through a cockpit selector or knob, manually setting the cabin altitude by opening or closing the valve.

Alternate pressurisation controller → INCORRECT. If the automatic pressurization system fails, the alternate controller is also inoperative.