A.0 B.非0 C.可為0或非0
A.關(guān)鍵項(xiàng)目 B.非關(guān)鍵項(xiàng)目 C.虛項(xiàng)目
A.關(guān)鍵項(xiàng)目B.非關(guān)鍵項(xiàng)目C.虛項(xiàng)目