IMAGINE YOU ARE GOING TO DRIVE ACROSS AN UNATTENDED LEVEL CROSSING...
35.Imagine you are going to drive across an unattended level crossing which has no lights
at all. What is the final thing you must do before actually crossing?
A.Open the near gate wide
B.Look to see if a train is coming
C.Telephone the nearest station
D.Listen for any animals approaching
As viewed from space, Earth’s distinguishing characteristics are its blue waters and white
clouds. Enveloped by an ocean of air consisting of 78% nitrogen and 21% oxygen, the
planet is the only one in our solar system known to harbor life. Circling the Sun at an
average distance of 149 million km (93 million miles), Earth is the third planet from the
Sun and the fifth largest planet in the solar system.
Its rapid spin and molten nickel-iron core give rise to an extensive magnetic field which,
coupled with the atmosphere, shields us from nearly all of the harmful radiation coming
from the Sun and other stars. Most meteors bum up in the Earth’s atmosphere before they
can strike the surface. The planet’s active geological processes have left no evidence of
the ancient pelting it almost certainly received soon after it was formed. The Earth has a
single natural satellite – the Moon.