Let radius of the semi-circle = $$r$$ cm => Area = $$frac{1}{2} imespi r^2$$=693$$ => $$frac{1}{2} imesfrac{22}{7} imes r^2=693$$ => $$r^2=693 imesfrac{7}{11}$$ => $$r=sqrt{63 imes7}=3 imes7=21$$ cm => Ans - (C)