From the four inner planets and our Moon, the strongest magnetic field is possessed by our own planet, the Earth. Earth's magnetic field is around 100 times stronger then that of Mercury, while the other two inner planets, Venus and Mars do not have their own magnetic fields.
'Climatic variations' and 'Human activities' can be regarded as the two main causes of desertification. removal of the natural vegetation cover（by taking too much fuel wood）, agricultural activities in the vulnerable ecosystems of arid and semi-arid areas, which are thus strained beyond their capacity.
The correct answer is - C. hot spots in the mantle.
The Hawaiian Islands are a volcanic islands. They are lying above a hot spot. The hot spot volcanoes, unlike the other ones, are far away from the boundaries of the tectonic plates and they are emerging on places were there's hot spots. These hot spots manage to penetrate through the crust and get the magma from the mantle up to the surface and create volcanic islands in meantime.
the capital of iran is Tehran or Teheran.
