Final answer:
The narrator wants to ask her mother to buy nylons for her birthday because she saw them in a store window.
Step-by-step explanation:
The narrator wants to ask her mother to buy nylons for her birthday because she saw them in a store window. The narrator mentions that she is influenced by the idea of having beautiful clothes and wanting to be happy, which is possibly reinforced by the images she sees in magazines and books. Therefore, the correct option is c) Because she saw them in a store window.