问题补充：
A number of art works are believed to having been stolen during the world war.这句句子的主谓宾是什么?
答案：
主：A number of art works
谓：are believed to
宾：having been stolen
状语：during the world war
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======以下答案可供参考======
供参考答案1:
主语是A number of art works
谓语 are believed to having been stolen during the world war.
因为是被动语态，实际主语没有，谓语是believed，实际的宾语是A number of art works
供参考答案2:
A number of art works主
are believed谓语动词
to having been stolen宾，这里的宾语是非谓语动词，可能你看起来比较奇怪，以后学了就好了，不懂再问吧
during the world war.状语
供参考答案3:
主语： a number of art works
谓语：are 。。。。后面全是。
宾语没有。意思是：在二战期间，许多艺术作品相信都被偷走了。
