Just as the tree is the unit of a forest and the book the unit of a library, ______ the molecule is the unit of matter.
----How did you find the party ? ----Perfect ! It ______ very well .
---Did you enjoy yourself at the party ? ----Yes , I’ve never been to _______ one before .
The message is very important , so it is supposed ______ as soon as possible .
______ is certain is that Bill will recover from his injury in time for the football match.
Some customers accuse Toyota ______ being slow to fix the car problems, which makes them disappointed.