wolf是以f结尾，所以变复数形式是把f变成v再加es；
wolf
n.狼；
v.大口地快吃;狼吞虎咽；
第三人称单数： wolfs；复数： wolves；现在分词： wolfing；过去式： wolfed
The wolf clawed at the tree and howled the whole night.
这匹狼用爪子挠着树，嚎叫了整晚。
It is 250 years since the wolf became extinct in Britain.
狼在英国已经灭绝250年了。
She was fed up with the builders' wolf whistles each morning.
每天早上都有建筑工人冲她挑逗地吹口哨，她烦都烦死了。
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