Nobody knows for sure how dinosaurs died out 65,000,000 years ago. It _______ because of sudden changes of their living conditions.

— Could I have a word with you, mum? — Oh, dear, if you ______.

--- Shall we meet at the station at 8 a.m.?--- In fact we _________. The train _________ until 10 a.m..

---I think _________________ in the morning is a good way to improve your spoken English. ---I agree with you.

---Lingling says Miss Yu has gone to Shanghai, _____ that be true?---It _____ be true because I saw her in the office just now.