问题补充：
The words that we should pay attention toon the blackboard.
A. is writing
B. being written
C. are written
D. writing
答案：
A. is writing
B. being written
(答案→)C. are written
D. writing
解析：
试题分析:此题考查that引导的定语从句的基本用法。此句的含义是我们应该注意的单词都在黑板上。它的主语是the words是复数形式而句子we should pay attention to是that引导的定语从句用来修饰主语the words，故谓语动词也要用复数形式，故选C
