(a) diameter of semicircle $$=2.8cm$$
$$\therefore$$ Perimeter $$=\pi r+2r=\dfrac{22}7\times 2.8+2\times 2.8=8.8+5.6\ cm=14.4\ cm$$
(b) Total perimeter $$=1.5+1.5+2.8+\pi r$$, where $$r=\dfrac{2.3}2=1.4cm$$
$$=1.5+1.5+2.8+\left(\dfrac{22}7\times 1.4\right)$$
$$=5.8+8.8=14.6\ cm$$
(c) Total perimeter $$=2+2+\pi r$$, where $$r=\dfrac{2.8}2=1.4cm$$
$$=4+8.8=12.8cm$$
Hence, it is clearly seen that the distance of (b) i.e., $$14.6$$ is the longest.