There has (0) ..a…. a fascination with the planet mars ever since science fiction began to be written (1)…….. novels about beautiful martian princesses or three-headed invaders became a successful way to make readers (2) …………a world of the imagination. now, there is even a mars society whose members have recreated martian conditions on earth. devon island (3)………… in the canadian arctic, a vast area which (4) ……… mountains, cliffs and canyons like those on mars. there is even a massive crater. scientists are (5) …………..advantage of these similar conditions to (6) …………………whether it would be possible for human beings to live on mars. on devon island, the volunteers are getting used (7) ………space suits all the time. they have to withstand the extreme temperatures that are also found on mars. in fact, mars is not so different from our own planet as most people (8)…………. there are four distinct seasons and the sun rises and (9)…………….. to create days and nights similar in length to ours. in the past, there must have been life on mars; scientists have discovered river beds where water (10) ……..and evidence that living organisms once existed there. then the systems that supported life (11) ……… perhaps a giant asteroid hit the planet and increased its distance from the sun so that temperatures dropped and mars (12)…….. a dead, frozen planet.0 a been b be c to be d being 1 a produce b having produced c to producing d producing2 a to enter b enter c entering d to be enter 3 a lies b lays c is lying d is laying4 a is possessing b is possessed c possesses d possessions5 a putting b getting c making d taking 6 a see b be seeing c finding out d be discover 7 a to wear b to be wearing c to wearing d to be worn8 a imagined bare imagining c imagine d imagination 9 a sets b is falling c downs d falls 10 a was used to run b used to running c was used to running d used to run 11 a fell down b did wrong c broke down d broke12 a turned from b turned into c turned down d turned up silk productionlarge-scale production of silk (0) ..a.. on huge 'farms' of a certain kind of moth. a cocoon of fine threads of silk (1) ….by the silkworm, which is the grub of this moth. this cocoon is a small tubular structure designed by nature for the grub (2)…….. while it develops.the cocoons are transferred from the farm to the factory, where, (3)………. peeled by machines, they (4)…… in large tanks of warm water in order to (5) ……………the tightly woven silk. in the next step, the threads of silk (6) ……off by hand-operated machines. this part of the process is known as 'reeling' and can only (7)…… out by highly experienced staff. silk production in the factory (8) ……… by the raising of the silkworms themselves on the farm. as soon as the eggs (9) ……..by the female moths, they are stored in incubators. the grubs (10) …………. only on mulberry leaves which are only available at a certain time of the year. thus, the eggs (11) ………to promote hatching, so that the silkworms are born at the same time as the leaves become ready (12) ……..picked.0 a depends b is depended c has been depended d is depend1 a is spinning b is spinned c is spun d are spun2 a to protect b to be protected c to be protect d to be protecting3 a being b been c having been d having4 a are floated bare float c floated d have been floated5 a be remove b be loosened c loosen d loosening6 a are wound b are winding c have wound d has been wound7 a carry out b be carry out c be carrying out d be carried out8 a is precede b is proceeded c is preceded d had preceded9 a are lay b are laid c has been laid d have been layed10 a are feed b are feeds c are fed dare being fed11 a must be heat b must be hot c must be heated d must to be heated12 a to b to have been c to be d to be

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