* "namely" must be used either before a noun or before a noun phrase / clause.
you can't use it directly before an independent clause.
because of this principle, you can't say "namely they vary...". however, "namely that they vary..." and "namely considerable variation" are both fine.
this kills (a) and (e).
A选项：首先，由于本选项的dated是过去分词（不可能是过去时，因为date理应是被动语态，若是谓语动词的过去时应该用were dated），所以其引导的部分应该同found in Puerto Rico in 1991平行。鉴于此，and dated at 34 million years old身前和身后的逗号是不应该加的（只有三者平行或者两个完整的句子间的and前才应该加逗号）。
The book review editor sent out a greater number of books than reviews he actually 。。。这里才是27
取反，这里是说unenthusiastic reviewers 准确的反映了book review的价值，那么A book of great worth will receive only good reviews.
露西的宽而浅的骨盆实际上比现代人类的圆形碗状骨盆更适合双足行走，C错误
The shape and configuration of various bones must likewise be modified to allow the muscles to perform these functions in upright walking.选D
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gross profit＝revenu－expenses