What important question do the various research techniques lack the ability to answer?

What important question do the various research techniques lack the ability to answer? Did consumers purchase the product because of viewing the producers ads?

Besides asking, where did you find out about us, it is very hard for a research team to use techniques to find out if they viewed the companies ad's before making the purchase. It's hard to know if they saw and actually watched the commercial on T.V. or if they read about it in the magazine on purpose. 

d is the correct answer.

b is incorrect because it makes food by itself

c is incorrect because us humans don't know how to produce their own food using the sun like plants.

a is incorrect because consumers can depend on carnivores for eating food for consumers to eat the dead organism. same thing with omnivores.

levels of production can be increased by technology while holding labor and capital constant, because increased technology makes the production process more efficient. subsequently, the lras curve is almost a vertical line, that can shift to the right, with an increase in technology.

the relationship between the lras curve and the ppc is that both can make the economy could grow. the ppc achieves that when it shifts outward because of more resources or technological advances while the lras curve shifts if more resources are developed or if there are technological advances.

the lras curve is a vertical line at an output level that represents the number of goods and services a nation can produce over a sustained period using all of its productive resources as efficiently as possible with all of the current technology available to it.

the production possibilities frontier (ppf) is a graphical device that is used for economic analysis of production decisions because the ppf measures the maximum possible combinations of two goods that an economy is capable of producing with its currently available resources and technology.