已知W的一种核素的质量数为18，中子数为10；X和Ne原子的核外电子数相差1；Y的单质是一种常见的半导体材料；Z的非金属性在同周期元素中最强。下列说法不正确的是(　　)

    In 1620, about half the USA was covered by forests. Today the forests have almost gone. A lot of good land has gone with them, leaving only sand. China doesn't want to copy the USA's example. We're planting more and more trees. We've built the " Great Green Wall" of trees across northern part of our country. The Great Green Wall is 7,000 kilometres long, and between 400 and 1,700 kilometres wide. It will stop the wind from blowing the earth away. It will stop the sand from moving towards the rich farmland in the south. More "Great Green Walls" are needed. Trees must be grown all over the world. Great Green Walls will make the world better.
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