Q71. The imaginary line on the earth’s surface, which closely follows the 180 ยบ meridian, is called the
Q72. The heavier silicates named as ‘Sima’ or silica + magnesium are most abundant in the
Q73. The highest mountains in Africa, which is not part of any mountains chain, is
Q74. The layer of the earth, immediately below the crust, is called
Q78. The Ice age ended about ____ years ago.

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