The rocket engine, with its steady roar like that of a waterfall or a thunderstorm, is an impressive symbol of the new space age.Rocket engines have __1__ powerful enough to shoot astronauts __2__ the earth's gravitational pull and __3__ them on the moon.We have now become __4__ space.
. l4 X1 u/ W! M Impressive and complex __5__ it may appear, the rocket, which was __6__ in China over 800 years __7__ , is a relatively simple device.Fuel that is __8__ in the rocket engine changes __9__ gas.The hot and rapidly __10__ gas must escape, but it can do so only __11__ an opening that __12__ backward.As the gas is __13__ with great force, it __14__ the rocket in the __15__ direction.Like the kick of a gun __16__ it is fired, it __17__ the laws of nature __18__ by Sir Isaac Newton when he discovered that“ __19__ every action, there is __20__ equal and opposite reaction.”
/ I6 r* N: {3 G z" v3 x 1.A.shown B.been C.appeared D.proved6 T. D8 I' D) W: K# M' G) F# [9 q
2.A.against B.despite C.beyond D.from
; {" J4 _" v. C8 a0 m1 Z0 l8 t 3.A.send B.land C.take D.carry9 s" C. G* f* X0 b8 J; H
4.A.travelers B.astronauts C.researchers D.explorers
+ b( q% [5 l- C2 z" p+ f 5.A.that B.so C.as D.sometimes1 {' ?4 N9 D% v- q' m
6.A.made B.discovered C.developed D.invented
# @- X1 u0 L1 k h 7.A.in advance B.before C.earlier D.ago
1 k r! s. C3 q- n* x 8.A.round B.contained C.stored D.burned3 Z8 i( ~3 Q; V0 Z5 o: G: T
9.A.as B.into C.for D.the
) Z6 p; S4 c$ `+ i' J# n- m' ]. H 10.A.heating B.escaping C.expanding D.conducting- _8 p5 e1 ? L/ R- R! U
11.A.in B.at C.by D.through& p/ S0 P' ]2 N, m+ e$ M
12.A.turns B.goes C.faces D.directs0 }5 o% r6 G) u! X# D
13.A.transmitted B.dispersed C.erected D.radiated
. Y: H% x8 n+ t, e! P 14.A.attracts B.leads C.pulls D.pushes0 z2 O" m* g. d* r' E: W
15.A.same B.other C.opposite D.wrong
- v0 p# G, d) D5 ^! H* j9 G 16.A.that B.when C.if D.although( n( {) O4 J; X2 H5 r6 v
17.A.states B.proves C.follows D.breaks
- m- m7 S4 K5 u7 K+ I. ]2 [! z 18.A.described B.discussed C.considered D.made. e3 P& H5 i/ T& \. k& n
19.A.like B.as C.with D.for6 S* ~- l! L. N( w
20.A.no B.an C.another D.theCloze
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