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14. Paleontologists believe that fragments of a primate jawbone unearthed in Burma and estimated at 40 to 44 million years old provide evidence of a crucial step along the evolutionary path that led to human beings.
A. at 40 to 44 million years old provide evidence of
B. as being 40 to 44 million years old provides evidence of
C. that it is 40 to 44 million years old provides evidence of what was
D. to be 40 to 44 million years old provide evidence of
E. as 40 to 44 million years old provides evidence of what was

1. 主谓一致(单复数) （一级排除B,C,E ）
fragments 。。。。。。。。provide

2. 简洁：(一级排除 C. E )
what was … 多余
Sth is sth.
Sth does sth.
Sth is what is sth. (错, 1. 不并列, 2. 用单个名词和what 从句的概念对称肯定不对)
例句
There is speculation that increasing cold weather was what may have been responsible for the Anasazi move from Mesa Verde to sites in other canyons.
(A) that increasing cold weather was what may have been
(B) whether increasing cold weather was what was
(C) that increasingly cold weather was what had been
(D) whether increasingly cold weather may have been what was（E）
(E) that increasingly cold weather may have been
speculation that,,,,,名词Be what…..be 前后的东东要是一个东东啊…

3.. Estimate to be / that/ at ？(词的用法     二级排除A）estimated to be ………  estimate 做被动，只能是 sth. be estimated to be.......Estimate that….. estimate 做主动，用estimate sth. that  B 中的estimated that it is      it 多余  
It is estimated that……
At+地点, at+点时间(点和线) 不能加年份的
金山词霸解释
Estimate  vt.  -mated, -mating估计，判断（常与that连用）估价，（常与at连用）估计
I estimate her age at 35.我估计她有35岁。
（与in连用）估计…到达