221. There are 5 ________ in the passage about nanometer(纳米) technology we have just read. Please tell me the general meaning of the first one.
-Oh, Mum, just a few minutes. -Hurry up, Harry. Or by the time you pack your belongings, the flight __________!
__________ I see him, he looks sad.
By the time you have finished this book, your meal __________ cold.
-Do you think that housing price will keep __________ in the years to come? -Sorry, I have no idea.
If you want to avoid the risks of passive smoking, you can ask the smoker not to __________ in front of you.