New Delhi, March 11 -- A QR code printed on the Central Board of Secondary Education (CBSE) Class 12 mathematics question paper led to the music video of "Never Gonna Give You Up" by British singer Rick Astley.It became a classic internet prank known as "rickrolling" even as the board maintained that the security of the question paper remains uncompromised.The mathematics board examination was held on March 9. Soon after the exam got over, images of the question paper began circulating on social media with students alleging that the QR code printed on it redirected them to the 1987 hit song's video on YouTube.htc...