问
Although the sea breaks up the waste, beaches may become polluted and fish may not be safe to eat.
to eat 是句子的什么成分？另外，从语义关系上看，fish 与 eat 乃是被动关系，但上句却用了 to eat，而没有用 to be eaten，这是怎么回事呢？
答
从语法上看,to eat 是形容词 safe 的补足语。从语义上看,它使形容词的意义变得完整。如果说...fish may not be safe(……鱼可能是不安全的),则语义是不明确的:鱼不安全?鱼被污染物污染致死?还是有被捕的危险?而...fish may not be safe to eat 的语义却是非常明确的:……鱼吃起来可能是不安全的。
那么,上面的句子为什么用 to eat,而不用 to be eaten 呢? 这是因为在某些形容词后面充当补足语的动词不定式的主动形式可以表示被动意义的缘故。例如,He is hard to convince. [他很难(被)说服。] 见 difficult,expensive, 。
[附注]对于上述结构中具有被动意义的动词不定式的主动形式还可以解释为它实际上隐含着一个泛指的逻辑主语:for anyone。
He is hard to convince. = He is hard for anyone to convince.
Fish may not be safe to eat. = Fish may not be safe for anyone to eat.