I’m definitely going to settle in the countryside when I retire. All the words have a similar meaning with the underlined word, Except ______.

Such a problem is＿＿＿＿difficult for a primary school student ＿＿＿. 

By the time I reach the age of sixty, I hope to be healthy enough to travel ___________ .

— Excuse me, where does Tom live? — He lives _____ to the train station.

So hard did he work that he __________made himself ill for a whole week.