He left____with my secretary that he would call again in the afternoon.He said he would keep___.
A words,his words
B word,his word
C a word,his word
D the word,his word

解释一下好吗？
另外顺便问 What does the coat cost?
这句说法对不对？

答案B无疑。
word表示“信息、消息”时是不可数的；而且不用冠词。that从句是它的同位语。老教材“拿破仑的三个问题”里有这么一句：Word came that ......。
keep one's word守信
“What does the coat cost?”表达方式的不合理，并不在于What，而是cost。就价格而言，动作发生后才用cost来表达。What did the coat cost?
当然，从名词用法看又当别论。What is its cost?是可以的。