题目内容：
根据下列句子，回答题When ∧art museum wants a new exhibit, ( 1 )an
It 0av~ buys things in finished form and hangs ( 2 ) never
them on the wall． When a natural history museum
wants an exhibition, it must often build it． (3) exhibit
A summary of the physical and chemical nature of life must begin,
not on the Earth, but in the Sun; in fact, at the Sun's very center． It is here
which is to be found the source of the energy that the Sun constantly pours41．______
out into space light and heat． This energy is librated at the center of42．______
the Sun as billions upon billions of nuclei of hydrogen atoms collide
with each other and fuse together to form nuclei of helium, and doing43．______
so, release out some of the energy that is stored in the nuclei of atoms．44．_____
The output of light and heat of the Sun requires that some 600 million
tons of hydrogen are converted into helium in the Sun every second．45．______
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, a form of electromagnetic radiation like light and
radio waves, only of very much short wavelength． This gamma radiation46．_____
is absorbed by atoms inside the Sun to be reemitted at slight longer47．_____
wavelengths． This radiation, in its turn is absorbed and reemitted． As the
energy filters through the layers of the solar interior, it passes through
the X-ray part of the spectrum eventually becoming light． At this stage,
it has reached that we call the solar surface, and can escape into space48．____
without being absorbed further by solar atoms． A very small fraction of
the Sun's light and heat are emitted in such directions that after49．_____
passing unhindering through interplanetary space, it hits the Earth．50．_____
第（41）题__________
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