With regards to implant of microchip, what people worry about rests upon ______.

参考解析：

细节理解题。根据文章第五段第二、三句“‘Mobile phones are much more dangerous to our privacy,’ says Pawel Rotter, a biomedical engineer at AGH University of Science and Technology in Kraków, Poland. ‘If hacked, phones can convert into the perfect spy with microphones, cameras and GPS. Compared to them, the privacy risks from RFID are really small.’”可知，“手机对我们的隐私构成的危险更大。”波兰克拉科夫的AGH科技大学（AGH University of Science and Technology）生物医学工程师帕威尔·罗特（Pawel Rotter）说，“如果被黑，手机就能变成一个配有麦克风、摄像头和GPS的完美间谍。与之相比，RFID的隐私风险真的很小。”故选C。