Space is a dangerous place, not only because of meteors(流星) but also because of rays from the sun . The atmosphere again acts --1-- our protective blanket on --2--. Light gets through, and this is essential --3-- plants to make the food which we --4--. Heat, --5--, makes our environments tolerable and some ultraviolet rays(紫外线的) penetrate the --6--. Cosmic(宇宙的) rays of various kinds come --7-- the air from outer space, but --8-- quantities of radiation from the sun are screened off. --9-- men leave the atmosphere they are --10-- to this radiation; --11-- their spacesuits or the walls of their spacecraft, if they are inside, --12-- prevent a lot of radiation damage. Radiation is the greatest known danger to explorers in --13--. Doses of radiation are measured in --14-- called "rems(雷目)". We all --15-- radiation here on earth from the sun, from cosmic rays and from radioactive minerals. The "--16--" dose of radiation that we receive each year is about two millirems; it --17-- according toswheresyou live, and this is a very rough estimate. Scientists have reason to think --18-- a man can --19-- far more radiation --20-- without being damaged; the figure of 60 rems has been agreed.
1. [A] for [B] with [C] on [D] as 2. [A] stars[B] sun [C] earth[D] space 3. [A] with [B] from [C] under[D] for 4. [A] use [B] live [C] eat [D] get 5. [A] again[B] also [C] besides [D] too 6. [A] environment [B] space [C] atmosphere [D] earth 7. [A] across [B] to [C] from [D] through 8. [A] valid[B] enormous [C] various [D] proper 9. [A] As soon as [B] As well as [C] As much as [D] As possible as 10. [A] shown[B] exposed [C] faced[D] covered 11. [A] but [B] because [C] so [D] so that 12. [A] get [B] make [C] have [D] do 13. [A] earth[B] atmosphere [C] space[D] environment 14. [A] pieces [B] units [C] parts[D] elements 15. [A] receive [B] accept [C] bring[D] catch 16. [A] conventional [B] common [C] general [D] normal 17. [A] shifts [B] converts [C] modifies [D] varies 18. [A] what [B] which [C] that [D] why 19. [A] put up with [B] keep up with [C] come up with [D] catch up with 20. [A] from [B] than [C] as [D] away
. The atmosphere again acts --1-- our protective blanket on --2--. Light gets through, and this is essential --3-- plants to make the food which we --4--. Heat, --5--, makes our environments tolerable and some ultraviolet rays(紫外线的) penetrate the --6--. Cosmic(宇宙的) rays of various kinds come --7-- the air from outer space, but --8-- quantities of radiation from the sun are screened off. --9-- men leave the atmosphere they are --10-- to this radiation; --11-- their spacesuits or the walls of their spacecraft, if they are inside, --12-- prevent a lot of radiation damage. Radiation is the greatest known danger to explorers in --13--. Doses of radiation are measured in --14-- called "rems(雷目)". We all --15-- radiation here on earth from the sun, from cosmic rays and from radioactive minerals. The "--16--" dose of radiation that we receive each year is about two millirems; it --17-- according toswheresyou live, and this is a very rough estimate. Scientists have reason to think --18-- a man can --19-- far more radiation --20-- without being damaged; the figure of 60 rems has been agreed. 
