1.date 確定年代
The skeleton has been dated at about 2000 BC.
這骨架的年代為公元前2000年左右
2.descendant 后代
These adaptations served their descendant well as they invaded land.
這些適應(yīng)機制在它們的后代進化成陸生生物時起了很好的協(xié)助作用
3.upper limit 上限
Remember: there is no official upper limit to how much a person can spend in a lifetime.
記住,一個人一生能花多少錢,沒有官方上限
4.a set of 一組
Most genes are regulated by a master set of genes.
大多數(shù)基因都是由一組主基因來調(diào)控的