It was essential that the system (work).
举一反三
- Engineers are carrying out essential __________ work on the main line to Cambridge.
- The work of Web crawling or spidering is the essential part of a search engine.
- Which of the following would not be classified as a knowledge work system?
- Establishment of a ______ insurance system is essential for economic reforms. A: accurate B: sound C: undisturbed D: safe
- Work is taken negative when the work is done by the system and heat is taken as positive when it is transferred into the system. （ ）