23. Mr. Smiths was busy writing a story, only ______ once in a while to smoke a cigarette.
In the market,vegetables are sold by ________ kilogram,I mean,by ________ weight.
—John has put forward ________ most challenging question for us to answer.—Yes,it really is.I have never heard ________ harder one.
The education of ________ young is always ________ hot and serious topic.
As ________ unemployment is very high at the moment,it's very difficult for people to find ________ work.
The operation is ________ success and the patient is now out of ________ danger.