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.
; f$ ], h- E7 [7 B) [ k 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. ( B* M2 V* \7 `9 w2 [
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.”(153words) : @7 p) D& n4 H7 H$ }" C
1 l& h5 _5 H+ v4 B 1.A.shown B.been C.appeared D.proved + C l8 |0 L3 u
2.A.against B.despite C.beyond D.from
' d0 c' [1 T% ^1 n3.A.send B.land C.take D.carry 2 H# [. g/ v ]' `' u" L/ d
4.A.travelers B.astronauts C.researchers D.explorers
8 i+ N, C! u- d: o5.A.that B.so C.as D.sometimes ! X- b, v/ z/ F! F
6.A.made B.discovered C.developed D.invented 2 ~3 P! ]& C( A. H9 v& j0 R0 W4 O/ A
7.A.in advance B.before C.earlier D.ago
k/ o+ L8 R" }9 j8.A.round B.contained C.stored D.burned 0 j' P8 h' X: g2 Y: S
9.A.as B.into C.for D.the 6 B6 P: H+ n- ?& ~
10.A.heating B.escaping C.expanding D.conducting 8 y; y, V. W. g3 |
11.A.in B.at C.by D.through ) c$ i9 U3 K; Y/ }" w6 L, w
12.A.turns B.goes C.faces D.directs 8 n# x& F1 u: j9 s2 d4 p4 W
13.A.transmitted B.dispersed C.erected D.radiated 2 p7 I" y8 r: |+ s5 ?
14.A.attracts B.leads C.pulls D.pushes
) r6 K+ j3 |2 w1 A0 e. M% U15.A.same B.other C.opposite D.wrong
: h1 u; J" ?5 \* U' m2 W' r16.A.that B.when C.if D.although - p C5 E8 X4 z6 G$ @
17.A.states B.proves C.follows D.breaks ) z* u2 n+ G4 E
18.A.described B.discussed C.considered D.made
5 k* {' f: ~+ [# W8 f2 f19.A.like B.as C.with D.for
7 H3 L7 {# B$ f8 P& J0 _20.A.no B.an C.another D.the |