Answer:
B. Shoppers no longer need to leave the house or spend hours at the mall to make purchases.
Step-by-step explanation:
The main idea of an excerpt or paragraph is the important point which the writer wants the readers to convey to the writer. The main idea is clarified, expanded and explained with the help of the supporting details. The supporting details illustrate the main point and help in explaining the detail in a much better way. Supporting detail supports the main idea in the writeup. In the above case, option B is the supporting idea which explains the main idea about online shopping.