Ever since mobile phones became widely used around the world， there have been concerns about how safe they are． All mobile phones give off a small amount of radiation when in use， which many believe could be a cause of cancer． However， two recently published studies tried to finally answer the question of whether using mobile phones actually brings a dangerous risk to humans．
Carried out by the US government， the studies exposed rats and mice to radiation over the course of two years． A small number of the rats were found to have developed heart tumors （ 肿 瘤 ） as a direct result of the radiation exposure． However， John Bucher， one of the study's authors， said that the animals were exposed to far more radiation than even the heaviest mobile phone user would usually be， reported The New York Times． Bucher also added that the findings didn't make him want to change his or his family's mobile phone usage habits．
Indeed， the US Food and Drug Administration said it believes that it has "not found enough evidence that there are negative health effects on humans" from mobile phone use． Although mobile phones do give off radiation， it's a different type of radiation than that given off by dangerous sources．
High-energy radiation - such as that given off by nuclear waste - is known to be very dangerous to humans as it is able to damage our DNA， leading to cancer or even death． On the other hand， low-energy radiation - such as the one given off by mobile phones - is considered to be harmless．
We're exposed to this all the time， as it's given off by everyday objects like WiFi routers （路由器）， televisions， and even bananas． Some argue that when it comes to human health， however， you can't be more concerned， even if the risk is only small． For those people， an earphone is advised when they are making phone calls and the time spent using mobile phones can be limited．
But don't worry： there's no need to take bananas off the menu．



What did the two recent studies by the US government discover？ ______

A. Radiation exposure could bring risks to animals rather than to humans．
B. Too much radiation exposure could lead to health problems．
C. Using mobile phones only increases the risk of heart diseases．
D. There is no link between mobile phone radiation and cancer．

Why did the author mention other types of radiation？ ______

A. To inform people of harmful radiation sources．
B. To explain how radiation affects our lives．
C. To show mobile phone radiation is not so dangerous．
D. To remind readers to keep away from radiation．

What does the author suggest by saying "there's no need to take bananas off the menu" in the last paragraph？ ______

A. People should use a mobile phone giving off radiation as little as bananas．
B. It's unnecessary for people to get rid of the mobile phone due to its radiation．
C. Bananas should be included in the menu for people to keep health．
D. Eating bananas can help people against radiation given off by mobile phones．