Swahili city$-$states along the East African coast have made positive steps toward expanding international commerce by

A$.$ Establishing an unchanging state language

B$.$ Outlawing the use of Arabic language

C$.$ Incorporating words from Arabic and European and Asian languages into their Bantu$-$based language

D$.$ maintaining only one cultural identity in the cities

E$.$ subsuming all the Bantu languages into one language