Given a list of words to remember, helen notices that half of the words are items from the kitchen, while the other half are items from the garage. she realizes that by the words into two groups, it will be easier to remember them.

Chunking.

Explanation:

Chunking is the process of dividing the information in groups to be easily remembered. Due to their similar traits or familiarity, the groups of words are easily remembered being separated with those that share the familiarity rather than when they are all mixed up. Such is the case with Helen and the items both from the kitchen and the garage. If she makes two separate groups out of the big list, dividing everything in groups of things that share similar traits or common aspects, she will have it easier at remembering everything.

the answer to your question is,

old stone age.

-mabel < 3