英语：单项选择练习（一）
1.It is difficult to judge what words are ______ and what words are not.
A.worth to look up B.worth being looked up
C.worth looking up D.worthy of looking up
解析：短语be worth后面要求跟动名词形式，且用主动形式表示被动的意思，而be worthy后的结构为of being done或to be done。答案：C
