Question

which of the following is shear stress?
when the forces are directed outward, increasing the rocks volume
when the forces are directed inward, reducing the rocks volume
when a rock mass is pushed in opposite directions
rocks do not experience compressional stress

Explanation:

Shear stress occurs when forces act parallel to a surface in opposite directions. Pushing a rock - mass in opposite directions fits this description. Forces directed outward cause tensional stress (increase in volume), forces directed inward cause compressional stress (decrease in volume). And rocks do experience compressional stress.

Answer:

When a rock mass is pushed in opposite directions