First of all, GDP does not include household production, production from the underground economy, intermadiate goods or intermediate servces. That is because we define GDP to be the total of all market values of all final goods and services in the country. Hence, the correct answer by the above definition cannot be d. The point of that definition is that household products cannot have a market value and that if we counted towards the GDP both the value of a Graphics Card and that of the PC, we would double count the value of the Graphics Card, thus overestimating the GDP. We see that the value of new houses are included in GDP since they need materials and services and they have a market value, so b is also excluded. Finally, we have shown that b is true but that this is a good thing and leads to a better estimate of total production; the correct answer is a. Here is an example. If there is an economy where in every house there is plenty of wood and people make wood dolls out of tradition, these dolls will not have a market value if they are kept by the people who made them. Nonetheless they are products too and everyone could just try to sell them the next day at a reasonable price; then, the GDP would get a bump out of nowhere, because it cannot account for household items or the underground economy.
