(c) the tension of the string when the bob is at point B.

To find the tension of the string when the bob is at point B, we can use the principles of equilibrium.

Step 1: Draw a free-body diagram of the bob at point B.

Step 2: Identify the forces acting on the bob. In this case, we have the weight of the bob acting downwards and the tension in the string acting upwards.

Step 3: Apply Newton's second law in the vertical direction. The sum of the forces in the vertical direction should be equal to zero since the bob is in equilibrium.

Step 4: Write the equation for the vertical forces. The weight of the bob is given by the formula W = mg, where m is the mass of the bob and g is the acceleration due to gravity. The tension in the string is unknown, so we can represent it as T.

Step 5: Set up the equation for the vertical forces. We have T - W = 0.

Step 6: Substitute the values into the equation. The weight of the bob is mg, and we can assume a value for the mass of the bob. The acceleration due to gravity is a constant value of approximately 9.8 m/s^2.

Step 7: Solve the equation for T. Rearrange the equation to isolate T: T = W.

Step 8: Calculate the tension in the string. Substitute the values for the weight of the bob and solve for T.

Step 9: Check your answer. Make sure the units are consistent and the magnitude of the tension is reasonable.

By following these steps, you can find the tension of the string when the bob is at point B.