| Space is a dangerous place, not only because of
meteors (流星) but also because of rays from the sun and other stars. The
atmosphere again acts {{U}} (62) {{/U}} our protective blanket on
{{U}} (63) {{/U}}. Light gets through, and this is essential
{{U}} (64) {{/U}} plants to make the food which we {{U}} (65)
{{/U}} . Heat, {{U}} (66) {{/U}}, makes our environments tolerable
and some ultraviolet rays (紫外线) penetrate the {{U}} (67) {{/U}}. Cosmic
(宇宙的) rays of various kinds come {{U}} (68) {{/U}} the air from outer
space, but {{U}} (69) {{/U}} quantities of radiation from the sun are
screened off. As {{U}} (70) {{/U}} as men leave the atmosphere they are
{{U}} (71) {{/U}} to this radiation; {{U}} (72) {{/U}} their
spacesuits or the walls of their spacecraft, if they are inside, {{U}} (73)
{{/U}} prevent a lot of radiation damage. Rad A. again B. besides C. also D. too 我来回答: 提交
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