The correct answer is D) metered-in circuit. In a metered-in circuit, the hydraulic fluid flow to the linear actuator is controlled at the inlet side, regulating the speed of extension. This is achieved by using a flow control valve that meters the incoming fluid flow, allowing the pump to operate at the system pressure. This type of circuit provides precise control over the actuator's extension speed. The other options are incorrect because: A) A metered-out circuit controls the fluid flow on the return side, regulating the speed of retraction. B) A bleed-in circuit diverts a portion of the fluid flow back to the tank, which is not the same as a metered-in circuit. C) A bleed-off circuit is used to relieve excess pressure in the system, not to control actuator speed.