Explanation
This is a memory sentence to help you remember the first six straight-chain dicarboxylic acids. Take the first letter of each word: Oh My, Such Good Apple Pie → O-M-S-G-A-P, standing for Oxalic, Malonic, Succinic, Glutaric, Adipic, and Pimelic acids. (Not Picric acid: that's an unrelated explosive nitrophenol, not a dicarboxylic acid at all. Pimelic acid, also called heptanedioic acid, is the correct sixth member of this series.)