---How amazing it is that astronauts are exploring outer space!---It’s a challenge, I guess, man against nature.
– Have you ever been to the city before?– No. This is the first time I _____ here.
_____ is necessary for us to tell him about the result.
Mrs Chen is very strict — we don’t dare to say a word _____ she asks us to.
– The lecture will begin at 4 o’clock in the afternoon, right?– Yeah, ____ you get there on time.
– Tom has made great progress in spelling.– So he has and _____.