Zero filling is the process of adding a string of zeroes to the end of an FID. The following puzzle aims at understanding how zero filling impacts the line shape of a doublet.
The following 1H NMR spectrum was collected with a total of 4K points (selective region is shown as spectrum E). Applying different amounts of zero filling will modify the line shape of the doublet. Which spectrum(a) offers visually the best line shape for the doublet?