Final answer:
The term 'Negev' refers to the desert region that stretches southward from the Sea of Galilee to the Red Sea in Israel, and is the correct term that signifies 'desert,' 'plain,' or 'wilderness' in the context of the question.
Step-by-step explanation:
The term that can mean "desert," "plain," or "wilderness," and refers to a geographic region descending through the valley southward from the Sea of Galilee to the Red Sea is d) Negev.
The Negev is a desert and semidesert region in southern Israel, encompassing various landscapes including craters, cliffs, and limestone mountains. It covers more than half of Israel's land area and is sparsely populated due to its arid conditions. Contrary to options such as 'oasis' which represents a fertile spot in a desert where water is found, or 'savanna' which is a large grassy plain ecosystem, particularly of the African region with sparse tree growth, the Negev represents the kind of ecosystems that can range from desolate wilderness to arid plains.