She changed so much that I could hardly ____ her when we met again after a separation of 20 years.
Particular attention must be paid ______ welfare, especially in the poor area.
At this time tomorrow ______ over the Atlantic.
—That must have been a lot of work. —Yeah, it us three days to finish it.
______ many times, he finally understood it.
Going on a trip into ______ space must be quite ______ exciting experience.