Question

according to the evolution of useful things, what caused the popularity of post - it notes?
a prior need for them
their varied styles
widespread availability
their varied uses

Explanation:

In "The Evolution of Useful Things", Post - it notes became popular because of their varied uses. Prior to their creation, there wasn't a specific prior need for them in the way they were developed (they were a serendipitous invention). Their styles are not the main reason for popularity, and widespread availability came after their usefulness was recognized due to varied uses.

Answer:

D. their varied uses