【单选题】According to the Spanish researchers, which of the following statements is true?
A.
The closer you are to a mobile phone, the greater your exposure to electromagnetic radiation.
B.
The closer you are to a mobile phone that is being used to send and receive signals, the greater your exposure to electromagnetic radiation.
C.
The amount of electromagnetic radiation reflected by metal is almost too small to be measured.
D.
You shouldn't stand close to people who are using their mobile phones in train carriages, buses, and lifts.