Which assembly helps to raise the crane to the correct height?

The two-stage boom assembly is integral to raising the crane to the correct height as it is designed with segments that can extend or retract. This assembly allows the crane operator to adjust the length of the boom according to the required lift height. By deploying the two-stage mechanism, the operator can effectively increase the reach and height at which loads can be lifted, crucial for a variety of lifting tasks.

Counterweights are used to balance the crane and prevent tipping but do not directly contribute to raising the crane’s height. The swing bearing allows the upper structure of the crane to rotate, which is essential for positioning the load but does not influence the height adjustment itself. Hydraulic lines are necessary for the operation of various crane functions, as they power hydraulic systems but do not serve the specific role of raising the crane's height directly. Thus, the two-stage boom assembly is the correct answer as it plays the primary role in height adjustment for lifting operations.