This is a very serious matter and the Chinese Academy of Sciences is trying to public awareness about it.
The baby is generally healthy, but every now and then he ______ a cold.
--- Each of the students, working hard at their lessons, ______ the book. --- So have I.
--- Who’s the man over there? --- It’s Jack. --- Oh? ______ in Italy.
--- Excuse me, sir. Would you do me a favour? --- Of course. What is it? --- I ______ if you could take me to the station.
-- How are you planning to travel to Shanghai? --- I ______ yet, but I ______ taking a train.