Which one of the following equations parametrically represents equation to a parametric profile ?
(A)   `x=3cost`;  `y=4sint`      (B)   `x^2-2=-2cost`;  `y=4cos(t^2/2)`      
(C)   `sqrt(x)=tant`;  `sqrt(y)=sect`      (D)   `x=sqrt(1-sint)`;  `y=sin(t/2)+cos(t/2)`