若方程 僅表示一條直線，則實(shí)數(shù)k的取值范圍是

            .

若方程 僅表示一條直線，則實(shí)數(shù)k的取值范圍是

            .

A.（-∞,13]                                   B.(-∞,0]∪{3}

C.(-∞,0)∪{3}                             D.{3}

若方程x+y－6+3k=0僅表示一條直線，則實(shí)數(shù)k的取值范圍是

A.k≤3                                                           B.k＜0或k=3

C.k=3                                                             D.k≤0或k=3