instrumental

adj. /ˌɪn.strəˈmen.təl/ C1

起重要作用的；有帮助的

Very important in helping to make something happen or succeed.

仙境例句

The White Rabbit was instrumental in the trial, for he found the paper with the verses.

白兔在这场审判中起了重要作用，因为是他找到了那张写着诗的纸。