Here, we can observe that the actual dimensions of the second figure is same as first figure.
But, it can be clearly seen that some of the blocks are removed from the first to make second solid.
So, as we can see, a volume of 2×1×2=4 cubic cm is removed from the first solid to make the second one.
Now, Total Volume removed =4 cubic cm
Volume of one cube =1 cubic cm
Thus, no. of cubes removed =41=4 cubes
Hence, 4 is the correct no. of cubes removed.