Essential

要

Ask, Blackmail, Brief, Coerce, Demand, Engage, Essential, Examine, If, Important, In, Investigate, Invite, Make, Midriff, Necessary, Necessity, Need, Ought, Require, Shall, Should, Stop, Summarize, Summary, Threaten, Waist, Want, Will

必備

Essential, Mandatory

要地

Essential, Strategic

不可或缺

Essential, Indispensable

十分必要

Essential, Necessary

必不可少

Essential

至關重要

Crucial, Essential, Extremely, Vital