---Fish need water to survive; _____ , we human beings rely on air to live.

There are citizens who support graffiti, saying it’s a welcome addition to _________ dull street.

When we sleep is      cultural as biological-and practices differ greatly round the globe.

There are forty five students in our class, and they are _____ interested in football.

You must attend the meeting ____ at ten o’clock, as it is scheduled—not a minute early or late．