physics force equilibrium (5m)

For an object in equilibrium, the three acting forces can form a closed triangle. This is the principle of triangle of forces.

Since in a triangle, the sum of lengths of any two sides must be longer than the third. Option B doesn't comply with this rule, as 1N + 2N < 4 N. Hence, the three forces in option B cannot form a closed triangle. In other words, they cannot keep an object in equilibrium.