Language is generative, which means that the symbols of a language
a.
remain fixed, limiting the messages one can say
b.
must adhere to a certain standard or set of rules
c.
can be combined to generate unique messages
d.
are used to represent certain ideas or events

A language uses symbols, which are sounds, gestures, or written characters that represent objects, actions, events, and ideas.
A language is generative, which means that the symbols of a language can be combined to produce an infinite number of messages. A language has rules that govern how symbols can be arranged.

A, c, and d are the answers