GMAT CR Determining the authenticity(诚实; 确实)of purported pre-Columbian artifacts is never easy.Carbon-14 datingof these artifacts is often impossible due to contamination by radioactivepalladium (which occurs naturally in the soils of Central

GMAT CR Determining the authenticity(诚实; 确实)of purported pre-Columbian artifacts is never easy.Carbon-14 datingof these artifacts is often impossible due to contamination by radioactivepalladium (which occurs naturally in the soils of Central
GMAT CR
Determining the authenticity(诚实; 确实)of purported pre-Columbian artifacts is never easy.Carbon-14 datingof these artifacts is often impossible due to contamination by radioactivepalladium (which occurs naturally in the soils of Central and South America).However,historians and anthropologists have evolved tworeliable criteria,which,utilized in combination,have proven effective fordating these artifacts.First,because authentic pre-Columbian artifactscharacteristically occur in a coarse,granular matrix that is shifted by majorearthquakes,they often exhibit the unique scratch patterns known as gridding.In addition,truepre-Columbian artifacts show a darkening in surface color that is caused bycenturies of exposure to the minute amounts of magnesium in the soil of the Americas.
The criteria above would be LEAST usefulin judging the authenticity of which of the following?
(A) An ax headof black obsidian,unearthed from a kitchen midden (贝冢,贝丘)
(B) A potterybowl with a red ocher design,found in the ruins of a temple
(C) A set ofgold ear weights,ornamented with jasper pendants
(D) A blackfeather cape from a king’s burial vault（D）
(E) Amulticolored woven sash found near the gravesite of a slave
我在A和D之间犹豫不决,为什么?

GMAT CR Determining the authenticity(诚实; 确实)of purported pre-Columbian artifacts is never easy.Carbon-14 datingof these artifacts is often impossible due to contamination by radioactivepalladium (which occurs naturally in the soils of Central
文中提到的两个标准是——
　　1、they often exhibit the unique scratch patterns known as gridding （被大地震的搬迁造成）史前古器物常常呈现出被称作网格的独特刮擦图案.
　　2、true pre-Columbian artifacts show a darkening in surface color 真正的哥伦布以前的史前古器物表面颜色呈现出暗色.
要求是用这两个标准鉴定选项中的古器物（The criteria above would be LEAST useful in judging the authenticity of which of the following?）
　　(A) An ax head of black obsidian,unearthed from a kitchen midden
　　虽然黑曜岩砍伐器头是从贝冢中挖掘出来的,但是黑曜岩是一种质地坚硬的宝石,不易刮擦,也不会变色.由于地下的黑曜岩随着多年的地下高压,含水份量较大,一般可以根据水合层的厚度可以定出黑曜岩工具的制作年代.因此以上标准不适合用来对黑曜岩器物断代.
　　(D) A black feather cape from a king’s burial vault
　　君主葬墓中发掘出来的黑色羽毛斗篷可能会在大地震中移动位置造成刮擦图案,也可能由于年代久远而呈现出对微量镁的曝露而导致的模糊不清的暗色（darkening）

so easy，如楼上给你翻译的如此详细，你跟着你的common sense就做出来了。

我这里只解释为何D不行。

1：black feather，所以darkening in surface colour无法鉴定；
2：同样，black feather，所以表面不会有scratch pattern。

因此选D。

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so easy，如楼上给你翻译的如此详细，你跟着你的common sense就做出来了。

我这里只解释为何D不行。

1：black feather，所以darkening in surface colour无法鉴定；
2：同样，black feather，所以表面不会有scratch pattern。

因此选D。

要搞清楚问题所问啊，A的斧头是可以通过gridding判断出来的。gmat不是考你专业知识的，如楼上所说，黑曜石不易刮擦，那要看用什么刮了。按照专业知识来判断，只有钻石这种“石头”无法被刮花。你要用钻石刮黑曜石，妥妥的刮烂掉。别多想，别钻牛角尖，这里考的是逻辑，谨记。

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