In "A Cup of Tea" by Katherine Mansfield, the complexity of Rosemary's character is best illustrated by option a. She appears to be self-centered in the store but later feels a desire to help Miss Smith.
Throughout the story, Rosemary initially comes across as somewhat self-absorbed and focused on her own desires, particularly when she is in the shop looking at luxury items. However, her encounter with Miss Smith brings out a different side of her character—one that shows compassion and a desire to assist someone in need. This internal conflict between her self-centeredness and her empathetic instincts adds depth to her character, making her more complex and multi-dimensional.