B 固定搭配 in a word 一句话,总而言之.
A项,with a word说了一个词（句话）,不常见,常见的是With the word, he jumped into water. 说着话,他跳进了水里.同after the words.
a和of都需要其他的动词辅助才可以和 a word连接,比如：
She was look at a word“B”她正在看一个字母B.
The meaning of a word grows as it's using 一个单词的意思随着其被使用而不断发展.