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In just a few years mobile 1_______ have become a common sight everywhere. Walk past any cafe and you 2_______ people chatting on their phones or sending text messages. However, some people are concerned that the signals these phones send out may be bad for our health. They worry that holding a mobile close to 3_______ head might have an effect on your brain. So, it may be a good idea 4_______ your ordinary phone when you can.