To solve this problem, we need to analyze the forces acting on the particle moving in a circle.$\\$Given:$\\$• A particle of mass $m$ is attached to a string of length $l. \\$• The particle moves in a circle with speed $v. \\$• The tension in the string is $T. \\$The particle is moving in a circle, which means it is undergoing centripetal acceleration.$\\$The centripetal force required to keep the particle moving in a circle is given by:$\\ F_{centripetal} = \frac{mv^2}{l} \\$This centripetal force is provided by the tension in the string.$\\$Therefore, the tension $T$ in the string must equal the centripetal force required:$\\ T = \frac{mv^2}{l} \\$Thus, the net force on the particle, which is directed towards the center, is simply the tension $T. \\$Since the tension provides exactly the centripetal force needed, the net force is zero.$\\$Therefore, the correct option is:$\\$Option 3: zero$\\$This means the net force on the particle, directed towards the center, is zero.