beamreader
答：你的句法学得不错，可惜没能翻译一下句子。
这题不仅要从句法上判断AB都行，更要从句意及词法上判断，A不合句意，不合逻辑！
其实，你的第二个解释我有异议：
sth. is such that-从句，我认这个that从句是“结果状语从句”，
The strength of the new material is such that it can stand heavy loads at high temperature.
=It is such a strong material that it can stand heavy loads at high temperature.
=The new material is so strong that it can stand heavy loads at high temperature
是的，是有that-从句作表语从句的例句比如：
What we all know is that the earth goes around the sun.
我们都知道的是，地球绕着太阳转。
原题句意为：
这种新材料的强度是这样的强以至于它能在高温下承受重压。
直译：这种新材料的强度是这样的，它能在高温下承受重压。
不过，从这个直译来看，你对such,that的解释，也是有道理的。
本句的主语是the strength of the material, 是这种新材料的强度，谓语是系动词is,
所以表语应该是讲这强度是什么或怎么样，而不是一个陈述的事实。
试译你的A句：
The strength of the new material is that it can stand heavy loads at high temperature.
这种新材料的强度是它能在高温下承受重压。
这叫主表不搭配，犯了逻辑错误，或者说修辞法上的错误，这是一个高级错误！
如果你将主语strength改成feature(特性），则选A就正确了。特性是什么呢？特性是：它能在高温下承受重压。
回答完毕，不懂可追问。
PS:原来小米和楼主对strength的理解是“优点”啊？如果这么去理解的话，则此题就有争议了。
问题归结为：strength究竟是“强度”还是“优点”，是只能一种解释还是两者皆通？
这是个好问题，但不一定是个好题目了。
感谢小米，让我清楚了：
先行词
1．定语从句的先行词是名词或代词；而同位语从句的先行词只能是名词，而且仅限于idea，plan，fact，theory，promise，hope，news，doubt，truth，information，suggestion，question， thought，belief，conclusion等少数名词。
参见：/view/179.htm
关于such作代词的用法，我在《牛津双解英汉词典》电子版上找到：
such, pron
1 person or thing of a specified kind
某类的人或事物.
(a) (referring back 用以复指前文)
Cricket was boring. Such (ie That) was her opinion before meeting Ian. 打板球没意思. 她在认识伊恩以前就是这种看法.
She's a competent leader and has always been regarded as such by her colleagues. 她是个很有能力的领导人, 她的同事一向都是这样认为的.
(b) ~ as to do
sth; ~ that... (referring forward 用以预指後文)
The pain in her foot wasn't such as to stop her walking. 她脚疼, 但还不至於不能行走.
The damage was such that it would cost too much money to repair. 损坏得很严重, 要用很多钱才能修好.
这里的(referring forward 用以预指後文)，是不是也可以理解为：that-从句就是such的内容呢？
从而支持了楼主的同位语从句说呢？?
Whose book is this? --> This is Tom's(/his) book.
Whose is this book? --> This book is Tom's (/his)
It is such a strong material that it can stand heavy loads at high temperature
-->The strong material is such that it can stand heavy loads at high temperature
大家看，这两句话中的such和this/whose的用法是不是类似啊？
即可以作限定词，放在名词前，也可以作代词单独使用。
既然前一句和that从句是结果状语从句，那么同样意思的下一句，that不也是结果状语从句吗？
所以，这个that-从句，究竟是同位语从句还是结果状语从句，可能有争议。
PS:
Strength of materials
From Wikipedia, the free encyclopedia
Mechanics of materials, also called strength of materials, is a subject which deals with the behavior of objects withstanding stresses and strains. This theory was established on the basis of mathematical modeling in first and second principal stress, specifically because types of stress state in construction parts such beam and shell are possible to approximate as one or two dimensional one. An important founding pioneer in mechanics of materials was Stephen Timoshenko.
Definition[edit]
In materials science, the strength of a material is its ability to withstand an applied stress without failure. The field of strength of materials deals with loads, deformations and the forces acting on a material. A load applied to a mechanical member will induce internal forces within the member called stresses. The stresses acting on the material cause deformation of the material. Deformation of the material is called strain, while the intensity of the internal forces is called stress. The applied stress may be tensile, compressive, or shear. The strength of any material relies on three different types of analytical method: strength, stiffness and stability, where strength refers to the load carrying capacity, stiffness refers to the deformation or elongation, and stability refers to the ability to maintain its initial configuration. Material yield strength refers to the point on the engineering stress-strain curve (as opposed to true stress-strain curve) beyond which the material experiences deformations that will not be completely reversed upon removal of the loading. The ultimate strength refers to the point on the engineering stress-strain curve corresponding to the stress that produces fracture.
1 [U] quality of being strong; degree of intensity of this 力量;
力气; 强度; 浓度
a man of great strength
强壮的男子
strength of character, mind, will 性格、 思想、
意志的坚强
regain one's strength after an illness
病後恢复体力
the strength of a rope, ie its ability to resist strain 绳子的强度
put on a show of strength, ie show how strong one is 显示力量
For a small woman she has surprising strength. 她个子虽小但力大惊人.
The strength of feeling on this issue is considerable. 在这个问题上表现出的情绪很强.
How is the strength of alcoholic drinks measured? 含酒精饮料的浓度是如何测定的?
=>Usage 见所附用法.
2 [C, U] that which makes sb/sth strong; particular respect in which a person or thing is strong 力量的源泉; 强点;
长处
the strengths and weaknesses of an argument
一论据的长处和弱点
Tolerance is one of her many strengths.
宽容是她的一个优点.
His strength as a news-reader lies in his training as a journalist. 他胜任新闻广播员的工作, 在於他有当过记者的锻炼.