Question

which fastening system is used to drive steel pins or threaded studs into masonry and steel?
air impact wrench
mini hammer drill
powder - actuated tool
pneumatic screw nailer

Explanation:

A powder - actuated tool is designed to drive fasteners like steel pins or threaded studs into hard materials such as masonry and steel. An air impact wrench is mainly used for tightening or loosening nuts and bolts. A mini hammer drill is used for drilling holes in masonry but not for driving such fasteners in the described way. A pneumatic screw nailer is for driving screws or nails in a different context (usually in wood - working or similar applications where the force requirement and material type are different from driving into masonry and steel as per the question).

Answer:

powder - actuated tool