题目

You get anxious if there’s no wi-fi in the hotel or mobile phone signal up the mountain. You feel upset if your phone is getting low on power and you secretly worry things will go wrong at work if you’re not there. All these can be called “always on” stress caused by smart phone addiction.For some people, smart phones have liberated them from the nine-to-five work. Flexible working has given them more autonomy in their working lives and enabled them to spend more time with their friends and families. For many others though, smart phones have become cruel mastersin their pockets, never 磁铁能够吸引________、________、镍等物质，磁铁的这种性质叫做________，具有磁性的物体叫做________．