Mark the item if the chinese invented it.
a.
compass
b.
gunpowder
c.
musical instruments
d.
refined process for porcelain making
e.
paper
f.
printing press

The items that the Chinese invented are the following ones: compass, gunpowder, refined process for porcelain making, and paper. So, the answer s are A, B, D, and E. Musical instruments existed long before the Chinese even started to create their civilization, whereas printing press was invented by Johannes Guthenberg, a German blacksmith in 1440.

high entry costs prevent new producers from entering the market.

explanation:

an oligopoly is a term used to clarify the structure of a particular market, industry, or organization. a market is considered oligopolistic or amazingly focused when it is shared between a few companies.

It can provide a social code to protect each citizen's future economical earnings. and then obviously defending the country from invading countries.