Are they their books?意思是什么

Are they their books？
意思是：是他们的书吗？
例句：
1.That is because banks are using market values for more of the assets they hold on their books, meaning their prices fluctuate like those of stocks.
那是因为银行将更多依据市值来计算其表内资产的价值，从而令这些资产的价值像股价一样起伏不定。
2.I have found that while many major banks are pretending to be open to new customers, in truth they are shrinking their books and effectively extending no new lines.
我发现，尽管许多大银行都装作向新客户敞开大门的样子，但真实情况却是:它们正收缩自己的资产负债表，实际上已不再发放新贷款。

帮2楼的朋友说明~

They-指书本
their-指书的拥有者

are they their books? 这些是他们的书吗?

在这里,their是形容词。

这是他们的书吗

它们（物体）是他们（形容词物主代词）的书么？
不知道是不是耶！不过希望能帮到你！！