#1 Yuan Dynasty unified China after a period of more than 300 years. ...
#2 The first paper currency to be used predominantly was Yuan's official banknote Chao.
#3 Yuan astronomer Guo made the most accurate calendar built till then in China.
#5 Novel was developed as a literary form.
All of the above as children could reach in to small spaces and kids could work more for less pay and adults are more likely to not do it due to the risks
The answer should be C.
Hope this Helps! :)
