20) C

By looking at the figures for Mirror from 2000 to 2015 (in the given table), we can see the sales reduced from around 2.2 m in 2000, to around 1.7m in 2005, to around 1.2 m in 2010 and then to around 0.9 m in 2015.

The first three declines (2.2 m to 1.7 to 1.2 m) are proportional, i.e. there has been a decline of 0.5m every 5 years from 2000 to 2010. Therefore, the line should roughly be a steep straight line from 2000 to 2010.

Lines 1, 2, 4 and 5 are not completely straight between 2000 and 2010. Line 3 is the straightest so C is the answer.