[单项选择]A summary of the physical and chemical nature of life must begin, not on the Earth, but in the Sun; in (67) at the Sun’s very center. It is here that is to be found the (68) of the energy that the Sun pours out into space is (69) The energy takes the form of light and heat. This energy is (70) at the center of the Sun as billions (71) billions of nuclei of hydrogen atoms (72) with each other and fuse together to form nuclei of helium, and in doing so, (73) some of the energy that is (74) in the nuclei of atoms. The (75) of light and heat of the Sun (76) that some 600 million tons of hydrogen be (77) into helium (氦) in the Sun every second. This the Sun has been doing for several thousands of millions of years. The nuclear energy is released at the Sun’s center as high-energy gamma radiation, (78) of electromagnetic radiation like light and radio waves, onl
A. strained
B. hided
C. stored
D. put