A summary of the physical and chemical
nature of life must begin, not on the Earth, but in the Sun; in {{U}} (67)
{{/U}} at the Sun’s very center. It is here that is to be found the
{{U}} (68) {{/U}} of the energy that the Sun pours out into space is
{{U}} (69) {{/U}} The energy takes the form of light and heat. This
energy is {{U}} (70) {{/U}} at the center of the Sun as billions
{{U}} (71) {{/U}} billions of nuclei of hydrogen atoms {{U}} (72)
{{/U}} with each other and fuse together to form nuclei of helium, and in
doing so, {{U}} (73) {{/U}} some of the energy that is {{U}} (74)
{{/U}} in the nuclei of atoms. The {{U}} (75) {{/U}} of light and
heat of the Sun {{U}} (76) {{/U}} that some 600 million tons of hydrogen
be {{U}} (77) {{/U}} into helium (氦) in the Sun every second. This the
Sun has been doing for several thousands of mil A. nature B. fact C. research D. addition 我来回答: 提交
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