下列有关地球的说法不正确的是( )。
A．地球的历史可划分为5个地质时代
B．迄今为止地球的年龄约有46亿年
C．地球上的六大板块时刻都在运动
D．地球上的氧气最初来自地球内部
参考答案：D
解析： 地球自形成以来可划分为5个地质年代，从古到今是：太古代、元古代、古生代、中生代和新生代(有些代还可进一步划分为若干纪)，A项正确。通过现代科学方法对古老岩石进行测定，人们得知地球约存在46亿年了，B项正确。全球岩石圈分为六大板块，即太平洋板块、欧亚板块、印度洋板块、非洲板块、美洲板块和南极洲板块，它们无时无刻不在运动，C项正确。在地球大爆炸的时候，地球上的大气成分主要是甲烷、氨气和氢气，后来随着微生物的繁衍，大气成分中二氧化碳含量渐渐增多，经过多年的演化，通过海里藻类及其他植物的光合作用，空气中渐渐有了氧气。关于氧气的来源从地理学来说是海洋，从生物学来说是光合作用，从能源学来说是太阳。故D项说法不正确。本题选D。
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