Words can represent people, objects, concepts and events; although the words are not actually the items. This shows that language is: a. always abstract.
b. always concrete.
c. the same as communication.
d. a system of symbols.
e. a linear system.

d. a system of symbols.

Explanation:

Language can be defined as symbolic form of communication. It can represent people, concepts or ideas, recreation of events and objects. The symbols can be in the form of verbal and non verbal gestures and can be in the form of writing. These symbols are chosen conventionally. The words in the language are the symbols and their correct interpretation is required in the language for communication.

answer; i believe that the correct answer is ( rivers);

the branch of biology that deals with the normal functions of living organisms and their parts.

the way in which a living organism or bodily part functions.