因为这里省略了it is ,
完整句子是When it is compared with the book I bought yesterday,the one borrowed from the libray doesn't seem interesting.===The one borrowed from the libray doesn't seem interesting when it is compared with the book I bought yesterday.
当与我昨天买的那书相比时,我从图书馆借来的那本似乎不怎么吸引人了.
it是代词,指的就是The one borrowed from the libray ,从图书馆借来的那本书
因为句子的主语是The one borrowed from the libray ,而后面也是同样的主语,这时候相同的主语可以 省略,所以就变成了when compared with.
compared这里是 ed形式,有被动的意味,一般主语是物,例如这里的book
而comparing 是ing形式,有主动的意味,一般主语是人,而且直接是comparing sth.
例如While comparing the book I bought yesterday,I found the one borrowed from the libray doesn't seem interesting.=======I found the one borrowed from the libray doesn't seem interesting while comparing the book I bought yesterday,这里主语就是人.
C 跟B类似,应该是Comparing the book I bought yesterday,I found the one borrowed from the libray doesn't seem interesting