钢瓶可以单个或成群使用。

Cylinders may be used individually or in groups.

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癌症：关于移动电话基台周围发生成群癌症病例的媒体报道或传闻加大了公众的关注。

Cancer: Media or anecdotal reports of cancer clusters around mobile phone base stations have heightened public concern.

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都是因为万圣节这几年在中国越来越火，一到这个时候就有成群兴奋的人们或装扮成幽灵，或装扮成小鬼，巫婆。

This is only because Halloween is becoming more and more popular, with hordes of revellers dressing up as ghosts, goblins and witches.

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