This is AI generated solution, please use it at your own discretion.

The correct answer is **hydraulic prop**. Here's why: * **Active Support:** Active support systems are designed to exert immediate and continuous resistance against strata movement. They actively work to prevent or minimize deformation. Hydraulic props fall under this category as they provide an immediate and adjustable load-bearing capacity right after installation and as the roof moves. * **Passive Support:** Passive support systems rely on the strata to deform before they become fully effective. They resist movement after it has already begun. Let's look at why the other options are passive: * **Wire Mesh:** Primarily used for surface support to prevent small rock fragments from falling. It doesn't actively resist strata movement. * **Shotcrete:** Provides a surface coating that consolidates the rock mass and prevents weathering. It gains strength over time and reacts to deformation rather than actively preventing it. * **Fully Grouted Roof Bolt:** Stabilizes the rock mass by tying together layers of rock. The bolts need deformation to be fully effective by mobilizing the shear resistance between the layers.

The correct answer is **hydraulic prop**. Here's why: * **Active Support:** Active support systems are those that apply a force to the rock mass to prevent or reduce deformation from the moment the excavation is made. They are designed to immediately counteract ground movement and maintain stability. * **Hydraulic Prop:** Hydraulic props actively exert force against the roof (or hanging wall) to resist the downward pressure of the overlying strata. This immediate and continuous support makes them an active support system. Let's look at why the other options are generally considered passive or semi-passive: * **Wire Mesh:** Wire mesh is a *passive* support system. It provides surface support, preventing small rock fragments from falling, but it doesn't actively apply force to the rock mass. It relies on the rock to be stable to begin with. * **Shotcrete:** Shotcrete (sprayed concrete) is generally *passive* once it sets. It provides a surface layer that bonds to the rock, helping to consolidate it and prevent weathering or unraveling. While application can impart some initial support, its long-term function is primarily passive. * **Fully Grouted Roof Bolt:** Fully grouted roof bolts can be considered *semi-active* or *passive*, depending on the pre-tensioning. While the bolt itself doesn't actively apply force after being installed, the grouting process fills the gaps and creates friction, improving the overall rock