The correct options are
B CM of a uniform semicircular ring of radius 2R/3 is 4R/3π from the centre.
D CM of a solid hemisphere shell of radius R is R/2 from the centre.
CM of a uniform semicircular disc of radius R=4R/3 from the centre
CM of a uniform semicircular ring of radius 2R/3=2(2R/3)=4R/3 from the centre
CM of a solid hemisphere of radius R=3R/8 from the centre
CM of a hemisphere shell of radius R=R/2 from the centre
So, options B & D are correct.