import three;

size(7cm);
currentprojection=orthographic(5,4,3);

triple pA=(2,2,0), pB=(-2,2,0), 
       pC=(-2,-2,0), pD=(2,-2,0),
       pS=(0,0,5);

draw(pS--pD--pA--pS--pB--pA);
draw(pD--pC--pS^^pC--pB,dashed);

label("$A$",pA,S);
label("$B$",pB,E);
label("$C$",pC,NW);
label("$D$",pD,W);
label("$S$",pS,N);