served for land (feudalism). went to battles with them and supported them
It means that the emperor is not wearing any clothes?
What exactly is the question? Please let me know, and I will try to answer. :)
(Basically, comment me the question, and I will change this response and answer you!)
Answer:
b.
Explanation:
It wouldn't be A because they all aren't scientific discoveries.
It wouldn't be C because barbed wire and windmills do not fall under the communication category.
It wouldn't be D because windmills are not transportation.
