Scissors, Pin, Knife, and Axe are
examples of wedges (a simple machine). Wedge is a simple machine that can
either separate/cut things apart or hold things together. Among the 4 options above, 3 of them can
separate things apart and 1 holds a thing together.
Scissors, Knife, and Axe separates things
while Pin holds things together.
Thus, the answer is pin.
Other examples of wedges that are used
for separating might be a shovel, a pick axe, a saw, a needle, or an ice pick. Other
examples of wedges that can hold things
together as in the case of a staple, push pins, tack, or a nail.