It is written clearly in the requirements that all passengers _______ check onto board thirty minutes before the plane takes off.
The factory was built in a secret place, around _________ high mountains.
---It looks as if he were drunk. ---So it does. _________
---How was _________ they discovered the entrance to the underground palace? ---Totally by coincidence.
---He will take you as well. ---But I’d rather he _________.
It is clear that the whole world is passing through a social revolution in which a central _____ must be taken by scientists and technologists.