Final answer:
The main idea of 'A Sweet Invention' is that Ruth Wakefield invented the first chocolate chip cookie.
Step-by-step explanation:
The main idea of 'A Sweet Invention' is that Ruth Wakefield was a cook who invented the first chocolate chip cookie. The passage discusses how she came up with the idea of adding pieces of semi-sweet chocolate to her cookie dough, and how it eventually became a popular treat. The other options presented in the question, such as the origin of chocolate chip cookies or the first cookie served by the Toll House restaurant, are not the main focus of the passage.
Learn more about Ruth Wakefield and the invention of chocolate chip cookies