that _________ (56)withstood a harder knock._________ (57)when there were more than about 30 holes per square centimetre did the wood?s performance drop off.
A uniform substance doesn?t cope well with knocks because only a small proportion of the material is actually _________ (58).All the energy from the blow goes towards breaking the material in one or two places，but often the pieces left _________ (59)are pristine(未经破坏的). But instead of the energy being concentrated in one place，the holes provide many weak spots that all absorb energy as they break，says Vincent.“You are controlling the places_________ (60)the wood breaks，and it can then absorb more _________ (61)，more safely.”The researchers believe the principle could be applied to any material- _________ (62)example.to manufacture lighter and more protective packaging.It could _________ (63)be used in Car bumpers，crash barriers and armour for military vehicles，says Ulrike Wegst， _________ (64)the Max Plank Institute for Mental Research in Stuttgart.But she emphasizes that you _________ (65)to design the substance with the direction of force in mind.“The direction of loading is crucial，”she says. 51 A in B since C for D at 52 A or B although C and D despite 53 A down B over C up D into
54 A knew B concluded C saw D thought 55 A no B per C each D every 56 A it B the idea C they D spruce 57 A if B Just C Only D Rarely
58 A effected B beaten C slapped D affected 59 A behind B beyond C for D in 60 A which B there C that D where 61 A water B air C energy D safety 62 A among B in C as D for
63 A also B besides C else D yet 64 A over B at C around D on 65 A have B must C should D had 参考答案：
51.答案为C for centuries表示几个世纪以来，注意在用现在完成时的句子里for后面跟一段时间，since后面跟一点时间。
52.答案为B 这里需要一个连接词，但要表达“虽然”这样的让步意义。
53.答案为c 树叶在树的上部，所以在树干里把水分送到树叶里去的管道应该说是run up the trunk，而不是run down the trunk。
54.答案为D 这里所说的仅仅是一个假设，注意情态动词might，表示这还仅仅是一种可能，后面说要对此进行test。
55.答案为A 除了no，其他几个选项根本不可能用在这里。 56.答案为A 这里需要一个单数的代词，代替spruce或者the wood。
57.答案为C Only放在when从句前面起强调作用，表示“只有当……时”，注意后面的句子是倒装的，就是因为用了Only的要求。
58.答案为D? affected受到影响，effect(效力，生效)在词形上容易和affect混淆。beat(打)，slap(打耳光)在这里毫不相干。
59.答案为A to be left behind是“被留下”的意思，又如：Those who were left behind were soon found bv the enemy.留下来的那些人很快就被敌人发现了。
60.答案为D 这里填入的是一个引导定语从句的连接词，因为先行词是places，所以应该选where。61.答案为C 这里都在讲能量的吸收，很自然这里应该填入energy。 62.答案为D for example(例如)，是个十分普通的固定的表达方式。 63.答案为A “也能用于……”，只有also可以考虑。
64.答案为B 表示在某个单位或机构任职用at。
65.答案为A 后面有to，所以不可能用must或should，have to表示“必须，不得不”。
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