In the sentence "In spoken languages units of sound and meaning are combined sequentially.", the word "sequentially" can be replaced by_____.

A．Because the Native American needed their own activity center.
B．Because of the police's bad and rude behaviour towards the Native American.
C．Because the Native American was segregated.
D．Because the American government realized the Native American's terrible living conditions.

A．It is to represent letters of the alphabet.
B．Finger spelling serves as a way to differ from spoken language.
C．Finger spelling means you can spell the word by fingers.
D．It is a convenient way to communicate with the other people.