Final answer:
Based on the CPI categories and information provided in the text, the top two categories shopped for on a mobile device are not explicitly indicated, making it impossible to accurately answer the student's question without additional data or clarification from the survey.
Step-by-step explanation:
The survey mentioned in the text does not directly indicate which categories are shopped for the most on a mobile device; however, it discusses the Consumer Price Index (CPI) categories which may relate to consumer spending patterns. The CPI includes categories like Food and Beverages, Housing, Apparel, Transportation, and Medical Care among others. From the provided context, we cannot ascertain the top two categories for mobile shopping specifically.
It's worth noting that during economic downturns as mentioned in the text, spending patterns shift, but the data points towards a decline in food spending and does not provide a clear indication of increased mobile shopping in a specific category. Therefore, based on the information given in the text excerpts, the top two categories shopped for on a mobile device is indeterminable without further clarification or additional data from the survey.