Answer
It is possible in situations 2 and 4 that the block is stationary
Work Step by Step
An object can only remain stationary when there are either no forces acting upon it, or equal and opposite forces acting upon it. Situation 2 has two forces directly opposite, so two equal forces will cause the block to stay stationary. In situation 4 the resultant force of F3 and F2 acts directly opposite to F1, so with correct magnitudes chosen the block will experience equal and opposite forces and will remain stationary.
