英语流利说 Level 4 Unit2 Part1 Listening Extinction Events 2
Scientistsestimatethattherehavebeenatleast5massextinctionsinthelast540millionyears.Theyalsobelievethatwehaveenteredanewextinctionevent.Speciesarebecomingextinctatamuchfasterratethanbefore.Insteadofast