Mayo 21st, 2017
Open Cloze 2
Una semana más os traigo otro ejercicio para practicar…poco más hay que decir, ya sabéis que cualquier duda me la podéis dejar en los comentarios, a ver cuan difícil os ha parecido en esta ocasión. Un saludo!
Would you like to (1) an astronaut? To do this, you must travel at least 50 miles (80 kilometres) above the surface of the earth. But even after you have done that you are still (2) the earth’s atmosphere. Indeed, there are at least 300 miles of air still (3) you and the true vacuum of space.
Most of what we think of as our atmosphere is actually the troposphere, that part of the atmosphere closest to earth. This is where (4) of our weather happens, and it is the only part of the atmosphere which has enough oxygen and warmth for humans to survive. (5) part of the atmosphere is about ten miles thick at the equator and slightly half that height at each of the poles.
(6) the troposphere is the stratosphere, which you have probably visited if you have travelled on an international jet liner. (7) there is another kind of ‘jet’ at this altitude. Huge rivers of air called ‘jet streams’ flow through the stratosphere, and the stratosphere contains the ozone layer which protects us (8) harmful ultraviolet rays which could otherwise make life on earth extinct. After the stratosphere is the mesosphere, and above that the ionosphere, (9) is important for radio communications (10) signals can be bounced off the ionosphere to different parts of the world.
Many people think that the atmosphere is mostly oxygen, (11) that is what we breathe. But in (12) oxygen makes up only about 21% of the atmosphere, and carbon dioxide, which we breathe out, makes up less than 1%. (13) three quarters of the atmosphere is nitrogen, which was expelled from inside the planet while it was still very volcanically active. We have a (14) of nitrogen in our bodies, but we do not get it directly from the atmosphere. (15) we get our nitrogen from plants which we eat.