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英语有个句子不是很懂,请指教

来源:学生作业帮 编辑:作业帮 分类:英语作业 时间:2024/05/29 02:19:01
英语有个句子不是很懂,请指教
The best signal depends not only on its brightness but also on how well it contrasts with the background against which it must be seen.
这个句子讲的是关于 动物的光信号
我的问题是against which it must be seen.中的against 后面引导的部分,是与前面哪个部分相对应?
how well it contrasts with the background against which it must be seen.
p.s.我主要是against 在这里的句子的逻辑关系不清楚了,请指教
最佳光信号不仅取决于物体的亮度,也取决于物体与其背景对比的好坏程度,当然物体在背景映衬之下是可见的.against是介词,后面的which指代前面的background,也就是The best signal depends not only on its brightness but also on how well it contrasts with the background,and it must be seen against the background.