Read the following passage and choose the best answer (A, B, C, or D) to complete the passage. Mobile phones emit microwave radio emissions. Researchers are questioning whether exposure to these radio waves might (21) _____ to brain cancer. So far, the data are not conclusive. The scientific evidence does not enable us to say with certainty that mobile phones are categorically safe. On the other hand, current research has not yet (22) _____ clear adverse effect associated with the prolonged use ...

Read the following passage and choose the best answer (A, B, C, or D) to complete the passage.

Mobile phones emit microwave radio emissions. Researchers are questioning whether exposure to these radio waves might (21) _____ to brain cancer. So far, the data are not conclusive. The scientific evidence does not enable us to say with certainty that mobile phones are categorically safe. On the other hand, current research has not yet (22) _____ clear adverse effect associated with the prolonged use of mobile phones.

Numerous studies are now going on in various countries. Some of the results are contradictory but others have shown an association between mobile phone use and cancer. (23) _____, these studies are preliminary and the issue needs further, long - term investigation. Until the scientific data is more definite, it is prudent for people to try not to use mobile phone for long (24) _____ of time. Don't think that hands free phones are any safer either. At the moment, research is in fact showing the (25) _____ and they may be just as dangerous. It is also thought that young people whose bodies are still growing may be at particular risk.

Researchers are questioning whether exposure to these radio waves might (21) _____ to brain cancer.