It is obvious that chemical pollution will lead to a threat to agriculture and food chain, which will ________threat human health.
At our factory there are a few machines similar to ______ described in this magazine.
—I really can’t thank you enough —.
—What’s the matter with Tim? —Oh, Tim’s cellphone was left in a taxi accidentally, never ____ again.
It was believed that things would get worse, but ____ it is they are getting better.
I ____ to go for a walk, but someone called and I couldn’t get away.