A

Step 1: Calculate the initial kinetic energy of the block at the highest point. The kinetic energy (KE) is given by the formula:

$KE = \frac{1}{2} mv^2$
where $m = 0.2 \, kg$ (200 g converted to kg) and $v = 4 \, m/s$.

Substituting the values:

$KE = \frac{1}{2} \times 0.2 \, kg \times (4 \, m/s)^2 = \frac{1}{2} \times 0.2 \times 16 = 1.6 \, J$.

Step 2: Calculate the change in potential energy as the block moves from the highest point to the lowest point.
The change in height ($h$) from the highest point to the lowest point is equal to the diameter of the tube, which is $2 \times r = 2 \times 0.1 \, m = 0.2 \, m$.
Therefore, the change in potential energy (PE) is given by:

$PE = mgh$
where $g = 10 \, m/s^2$. Substituting the values gives:

$PE = 0.2 \, kg \times 10 \, m/s^2 \times 0.2 \, m = 0.4 \, J$.

Step 3: Use the work-energy principle. The work done (W) by the tube on the block is equal to the change in kinetic energy plus the change in potential energy.
Initially, the block has kinetic energy and as it descends, it loses this kinetic energy and gains potential energy. When it stops, all kinetic energy is converted to potential energy:

$W = KE - PE = 1.6 \, J - 0.4 \, J = 1.2 \, J$.

Step 4: The work done by the tube on the block is negative since it is the work done against the gravitational force as the object moves to the lowest point.
Therefore, the work done by the tube on the block during this process is -1.2 J.