Solution:In the figure, there are three semicircles, where the diameter of one semicircle is 56 cm.
The radius of a semicircle is .
The circumference of the semicircle is, .
Similarly, for a semi-circle which has diameter 28 cm, the radius is .
For the third semicircle, it is also 44 mm.
So, the boundary of the shaded region is,
Hence, the correct option is 4.