For this achievement you need to pick up 3.5 million points. The best way I found to get this achievement is by playing on the mountain map and getting as minimum dots as possible and picking up the fruit as soon as it appears using the bomb, My reasoning behind this is that you get the most of your points from killing the ghosts and in the later stages of the level there are a lot more ghosts to kill and therefore a lot more points to gain. Below I have posted my video example of gaining an A on the 2nd level I didn't use the tactic I have included here for this video but it gives you an idea of what you need to do to get an A