●Suppose we have the relation schema R(A,B,C,D)with functional dependencies;F{A→B,B→C,C→D,

●Suppose we have the relation schema R(A，B，C，D)with functional dependencies；F{A→B，B→C，C→D，D→A}，then R(A，B，C，

D．at least is in (73) ．

(73) A．1NF

B．2NF

C．3NF

D．BCNF