ph.
1. The river has narrowed down over the past 20 years.
这条河在过去的二十年变窄了许多。
2. Their demands had narrowed down to only two points.
他们的要求已减少到只有两点。
1. 缩小范围：但是这帮鸟人不是盖的,他们知道如何缩小范围(narrow down)去找到那种肽. (后面还出了一道选择题我选的是know exactly what to find. i am 100 percent sure.)好了,他们开始试验神经系统的肽(neuropeptide)并发现此酶对人体中的神经肽破坏速度甚快.
2. 缩小或限制范围(使更确切)：much less更不用说;更少;不及 | narrow down缩小或限制范围(使更确切) | not to mention更别提...,更不必说...
3. 变窄：narrow capillary segment 毛细管颈 | narrow down 变窄 | narrow examination 严格的检查
4. 缩小：6. require that sb. (should) do sth. 要求某人应该做某事 | 7. narrow down 缩小 | 8. have no skill at doing 不具备什么的技能
verb
1. become more focus on an area of activity or field of study
e.g. She specializes in Near Eastern history
Synonym: specializespecialisenarrow
2. define clearly
e.g. I cannot narrow down the rules for this game