Answer:
A market for cats would have had a positive externality.
Because the cats would kill the rats on sight since that is their natural behavior.
However, it is interesting to mention, that the cat's killing has been more of a "mythic" aspect of this story, since it fails to take into account that since the black death was caused by the<em> yersinia pestis</em> bacteria, cats could have been also infected, and since their interactions with humans are greater than rats or fleas, the real outcome could have been totally unexpected.
I believe the answer is: <span>tiered lessons
</span><span>tiered lessons refers to a study approach that is aimed to make student in the class to utilize various cognitive skills in order to tackle different problems.
This approach is used to make the class become more flexible and not forcing the children to stick into one specific way of learning.</span>
The correct answer is C. quotation marks
Using quotation marks forces the search engine to search only for websites that have that specific phrase. If you don't use them then it will also search for those websites that have only parts of the phrase, but using the marks makes it better for your search.
