单选题

　　【阅读理解】Mobile phones should carry a label if they proved to be a dangerous source of radiation, according to Robert Bell, a scientist. And no more mobile phone transmitter towers（发射塔） should be built until the long-term health effects of the radiation they emit（放射） is scientifically evaluated, he said. "Nobody’s going to drop dead overnight but we should be asking for more scientific information," Robert Bell said at a conference on the health effects of low-level radiation. "If mobile phones are found to be dangerous, they should carry a warning label until proper shields can be devised," he said.

　　Q：According to Robert Bell, if mobile phones prove to be dangerous to people's health

　　A、they should be banned immediately.

　　B、the use of them should be restricted.

　　C、all transmitter towers should be torn down.

　　D、a warning label should be attached.