7.But these factors do not account for the interesting question of how there came to be such a concentration of pregnant ichthyosaurs in a particular place very close to their time of giving birth.
(Of 结构作定语：of how there came to be such a concentration of pregnant ichthyosaurs…)
但这些因素并不能解释这个有趣的问题：为何在一个特定的地点会如此集中地出现即将临产
的怀孕鱼龙群。
分句 1：But these factors do not account for the interesting question
分句2：of how there came to be such a concentration of pregnant ichthyosaurs in a particular place
very close to their time of giving birth
分句 1 嵌套分句 2.分句 2 是 Of 结构作后置定语修饰说明 question 的内容。
8. Amid rumors that there were prehistoric mammoths wandering around the unknown region and that somewhere in its wilds was a mountain of rock salt 80 by 45 miles in extent，the two captains set out.
(同位语从句 rumors that…)
当时有一些传言，说有史前的猛犸在这一陌生的区域活动，而且在这一区域的某个地方有一
座巨大的盐石山，其面积达 80 英里长 50 英里宽。就在这些传言中，两位上尉出发了。
分句 1：Amid rumors
分句 2：that there were prehistoric mammoths wandering around the unknown region
分句 3：and that somewhere in its wilds was a mountain of rock salt 80 by 45 miles in extent
分句 4：the two captains set out
分句 1 和分句 4 构成倒装，正常的语序应该是分句 4+分句 1，即 the two captains set out Amid rumors。分句 1 嵌套分句 2 和分句 3，分句 2 和分句 3 是修饰分句 1 的 rumors 的同位语从句，
用来说明谣言的具体内容。分句 2 和分句 3 构成并列关系。
9. In the seventeenth century the organ, the clavichord，and the harpsichord became the chief instruments of the keyboard group，a supremacy they maintained until the piano supplanted them at the end of the eighteenth century.
(同位语 a supremacy)
17 世纪时风琴、敲弦琴和拨弦琴成为键盘乐器类的主要成员，这种至高无上的地位一直由
它们保持，直到 18 世纪末被钢琴所取代。
分句 1：In the seventeenth century the organ, the clavichord，and the harpsichord became the chief instruments of the keyboard group，
分句 2：a supremacy they maintained until the piano supplanted them at the end of the eighteenth century
分句 2 是分句 1 的同位语从句，用来修饰说明分句 1 中的 the chief instruments of the keyboard group