Answer the following question: Read the following article and answer the question. Article: Here's one number to keep in mind during your next cell phone conversation: 50. A new experiment shows that spending 50 minutes with an active phone pressed up to the ear increases activity in the brain. This brain activity probably doesn't make you smarter. When cell phones are on, they emit energy in the form of radiation that could be harmful, especially after years of cell phone usage. Scientists don't know yet whether cell phones are bad for the brain. Studies like this one are attempting to find it out. The 47 participants in the experiment may have looked a little strange. Each one had two Samsung cell phones attached to his or her head -- one on each ear. The phone on the left ear was off. The phone on the right ear played a message for 50 minutes, but the participants couldn't hear it because the sound was off. With this set-up, the scientists could be sure they were studying brain activity from the phone itself, and not brain activity due to listening and talking during a conversation. After 50 minutes with two phones strapped to their heads, the participants were given PET scans. The PET scan showed that the left side (the side with the phone turned off) of each participant's brain hadn't changed during the experiment. The right side of the brain, however, had used more glucose, which is a type of sugar that provides fuel to brain cells. These right-side brain cells were using almost as much glucose as the brain uses when a person is talking. This suggests that the brain cells there were active -- even without the person hearing anything. That activity, the scientists say, was probably caused by radiation from the phone. Henry Lai, who works at the University of Washington in Seattle, is uncomfortable with the data related to cell phones. Holding a cell phone to your ear during a conversation is "not really safe," Lai told Science News. Lai is a bioengineer at the University of Washington in Seattle. He wrote an article about the new study for a journal, but he did not work on the study.... Question: Which of the following statement is true? Answer:

OPTIONS: a). Scientists are sure that cell phones are bad for the brain. b). In the experiment, the left side of the brain used more glucose. c). Radiation from the phone probably causes the change in the brain. d). Henri Lai wrote a lot of articles about this new study.
Answer:
c).