Tom ____ skating, so he spends all his spare time on it.

(2013·乌鲁木齐高三第一次诊断性测验)That scientist ________ work is successful has been made a model worker.

After all of us finished our homework, the teacher told us _________at once.

It is difficult for us to learn a lesson in life we’ve in fact had that lesson.

On the table _____ two dictionaries．You may look up the word in either of them．