"of necessity, necessarily," in archaic constructions involving must (late 14c.) is from Old English nede, instrumental and genitive singular of nied (see need), used as an adverb reinforcing must, hence the genitive ending.
权威例句
1. There needs to be a properly informed public debate.
有必要让公众在充分知情的状况下展开辩论。
2. Don't assume your baby automatically needs feeding if she's fretful.
不要想当然地认为你的宝宝一闹就是要吃奶。
3. Choose a soft, medium or firm mattress to suit their individual needs.
针对他们各人不同的需要挑选柔软、软硬适中或者坚硬的床垫。
4. The European Parliament badly needs a president who can burnish its image.
欧洲议会急需一位能改善其声望的主席。
5. The economy needs an immediate 2 per cent cut in interest rates.