Of all systems of symbols,language is the
most highly developed.It has been
pointed out that human beings,
_____,can make anything stand for anything.
Human beings have agreed,in the course
of centuries of mutual dependency,
to let the various noises that they can
Produce with their lungs,throats,tongues,
teeth,and lips systematically stand for
certain happenings in their nervous systems.
We call that system of agreements language.
(A)by nature(B)by definition (C)by agreement
(D)by blood
答案是C我選A
實在是不知道為什麼是(C)協定地
請高手解答謝謝