An example of a memory aid is C. A "cellar" is often dark. Both words contain -ar.
This is because memory aids are something that help you to remember a fact or another piece of information. It is important that they be unique, so that they will help you remember information you would otherwise forget. The fact that cellar and dark share two letters allows you to see a common connection between them, hopefully triggering your memory to let you know that cellars are dark.
Option D isn't correct because it is just a definition. It is a good idea to check the dictionary for spellings, but that most likely will not help you to remember them, so Option A isn't correct, either. Option B is also incorrect because it is grouping similar words together, but not providing you with any new information. Therefore, your answer is Option C.
