The structures of many proteins—and their constituent domains—are so stable and effective that they have been conserved throughout evolution among many diverse organisms.
举一反三
- They have been very good friends for so many years, but they have nothing ______ common.
- Never before _______ so many restaurants offering food delivery. A: there are B: there have been C: were there D: have there been
- There has been a sharp __________ in profits this year, so some companies have dismissed many employees.
- ______ so many people put of work as today. A: Before have never there been B: There have been never before C: Never before have there been D: Have there never before been
- If you had been more (care) ______, you wouldn’t have made so many mistakes.