Less Is More
It sounds all wrong--drilling holes in a piece of wood to make it more resistant to knocks.But it works because the energy from the blow gets distributed throughout the wood rather than focusing on one weak spot.The discovery should lead to more effective and lighter packaging materials. Carpenters have known ________centuries that some woods are tougher than others.Hickory，for example，was turned into axe handles and cartwheel spokesbecause it Can absorb shocks without breaking.White oak，for example，is much more easily
damaged，_________ it is almost as dense.Julian Vincent at Bathe University and his team were convinced the woods internal structure could explain the differences.
Many trees have tubularvessels that run _________ the trunk and carry water to the leaves.In oak they are large，and arranged in narrow bands，but in hickory they are smaller，and more evenly distributed.The researchers _________ this layout might distribute a blows energy throughout the wood.soaking up a bigger hit.To test the idea，they drilled holes 0.65 millimetres across into a block of spruce，a wood with _________ vessels，and found that _________ withstood a harder knock._________ when there were more than about 30 holes per square centimetre did the woods performance drop off.
A uniform substance doesnt cope well with knocks because only a small proportion of the material is actually _________ .All the energy from the blow goes towards breaking the material in one or two places，but often the pieces left _________ are pristine.
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_________ the wood breaks，and it can then absorb more _________ ，more safely.The researchers believe the principle could be applied to any material- _________ example.to manufacture lighter and more protective packaging.It could _________ be used in Car bumpers，crash barriers and armour for military vehicles，says Ulrike Wegst， _________ the Max Plank Institute for Mental Research in Stuttgart.But she emphasizes that you _________ 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在词形上容易和affect混淆。beat，slap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，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。