以下哪一項(xiàng)正確定義了等級關(guān)系？A．戰(zhàn)略計(jì)劃，項(xiàng)目，項(xiàng)目集和項(xiàng)目組合B．項(xiàng)目，項(xiàng)目集，戰(zhàn)略計(jì)劃和項(xiàng)目組合C．項(xiàng)目組合，項(xiàng)目集，戰(zhàn)略計(jì)劃和項(xiàng)目D．戰(zhàn)略計(jì)劃，項(xiàng)目組合，項(xiàng)目集和項(xiàng)目
