是必要的it: it2 pron. (sing. Nom. ...necessary: adj. 必要的,不可缺的;必须的,强迫的;必然的,必定 ...that: pron. (pl. those ) 1.〔指示代名词〕 ...s: the collar of S [SS, S ...be necessary to: 对…有必要下载手机词典可随时随地查词查翻译