A horrible thought _________ him when he was waiting for Tom in the airport: what if the plane from Malaysia had been hijacked（劫持）?

(2014·安徽省芜湖三校一模)A recent study has  ________an unexpected conclusion that the African elephant should be divided into two different species.

The search was________ when night came，even though the child had not been found.

I had wanted to take the career of being a model, but I ________ not good at dealing with constant media attention.

Doctors ___ the old man not to smoke so much, but he just couldn’t give it up.