The diameter of the gravity disc is too big It causes oil to flow through the water outlet We changed the disc and no （） is found in the water outlet.

A . the deck line B . Plimsoll disc C . Plimsoll line D . summer load line

A . Ⅰ only B . Ⅱ only C . both Ⅰ and Ⅱ D . neither Ⅰ nor Ⅱ

A . the crank-web B . the connecting rod C . the main bearing D . the cross-head

A . piston gudgeon pin B . piston skirt C . cross-head D . cross-head pi

A . larger than B . smaller than C . equal to D . none of the above

A . takes B . is C . has D . make

A . A B . B C . C D . D

A . less than B . greater than C . equal to D . twice larger tha

A . the crosshead B . the journals of the crosshead C . the crosshead shoes D . the guide

A . bowl periphery B . bowl center C . upper surface D . lower surface

A . Tides B . Sea C . Swell D . Wind

A . center of buoyancy B . center of flotation C . center of gravity D . tipping center

A . greater B . better C . smaller D . le

A . avoid unnecessary pints inventory B . keep torsional vibration constant C . use existing supports and braces D . maintain specified injection characteristic

A . a micrometer B . a bridge gauge C . a spanner D . a wrench

A . 125 mm B . 183 mm C . 215 mm D . It depends on outside pipe diameter

A . thinner B . thicker C . smoother D . rougher

A . a bolt B . a cap C . a disc D . a nut

A.重力是万有引力中特殊的一种力，重力属于万有引力； Gravity is a special force in the Universal Gravitation, Gravity belongs to the Universal Gravitation;B.重力就是万有引力，万有引力就是重力； Gravity is Universal Gravitation, and Universal Gravitation is Gravity;C.重力不是万有引力，重力与万有引力是两种力； Gravity is not Universal Gravitation, Gravity and Universal Gravitation are two kinds of forces;D.以上都不对； None of the above is true;

Scientist 1 The object was a comet, a body made of ices (such asfrozen water or methane) and dust. Most of this cometarymaterial is volatile(easily vaporized) and low in density.Friction in Earth’s atmosphere heated the comet to a tem-perature at which it exploded, high above the ground. Themajority of the ices and dust were vaporized in the explo-sion, which explains why no crater was formed at the siteand why no large, identifiable fragments of the object werefound. An asteroid would not have been completelydestroyed. Intact asteroid fragments that reached theground would have created one or more craters uponimpact and left behind recoverable pieces. Evidence showsthat the object decelerated rapidly before it exploded.Because of their low density, comets are capable of suchrapid deceleration, whereas high-density objects, such asasteroids, are not. Scientist 2 The object was a stony asteroid. As it entered Earth’satmosphere, its high speed created a large air pressure dif-ference between the area just in front of the asteroid andthe area just behind the asteroid. The large pressure differ-ence eventually exceeded the structural strength of theasteroid. The asteroid flattened, decelerated rapidly due tothe dramatic increase in its surface area, and fragmentedbefore reaching the ground. This fragmentation would haveappeared like an explosion. Calculations show that a cometbetween 10m and 100m in diameter would explode at analtitude much higher than 8km, but a stony asteroid of thatsize would fragment at or near an altitude of 8km.Recovery of large asteroid fragments is difficult due to thearea’s boggy soil; however, small, glassy fragments wererecovered and are believed to be melted and resolidifiedpieces of the asteroid. Which of the following phrases best describes the majorpoint of difference between the 2 scientists’ hypotheses？ A.The location of the event B.The speed the object was traveling C.The density of Earth’s atmosphere D.The type of object that entered Earth’s atmosphere

是 否

是 否

Impressive and complex 13 it may appear, the rocket, which was invented in China over 800 years 14 , is a relatively simple device.Fuel that is burned in the rocket engine changes 15 gas.The hot and rapidly expanding gas must escape, but it can do so only 16 an opening that faces backward.As the gas is 17 with great force, it pushes the rocket in the 18 direction.Like the kick of a gun when it is fired, it 19 the laws of nature described by Sir Isaac Newton when he discovered that“ 20 every action, there is an equal and opposite reaction.” 11.A.shown B.been C.appeared D.proved 12.A.send B.land C.take D.carry 13.A.that B.so C.as D.sometimes 14.A.in advance B.before C.earlier D.ago 15.A.as B.into C.for D.the 16.A.in B.at C.by D.through 17.A.transmitted B.dispersed C.erected D.radiated 18.A.same B.other C.opposite D.wrong 19.A.states B.proves C.follows D.breaks 20.A.like B.as C.with D.for